Monday, December 04, 2006
Hiyam's Journal Update
Chemistry - A European Journal Volume: 12, Issue: 33 November 15, 2006
Computational Modeling of Polyoxotungstates by Relativistic DFT Calculations of 183W NMR Chemical Shifts 183W NMR Chemical Shifts.
Thursday, November 16, 2006
Joel's other journal updates
Not much from the other journals regarding SSNMR but there are some interesting systems. I have summary files for all the articles that I've collected so if you want to see them let me know.
Here's one article with NMR. Anyone interested?
Local Environments and Dynamics of Hydrogen Stoms in Protonated Forms of Ion-Exchangeable Layered Perovskites Estimated by Solid-State 1H NMR.
S. Tani, Y. Komori, S. Hayashi, Y. Sugahara.
JSolidStateChem (2006) 179, 3357.
Abstract:
The local environments and dynamics of hydrogen atoms in five samples of protonated forms of ion-exchangeable layered perovskites, Dion–Jacobson-type H[LaNb2O7] and H[LaTa2O7], Ruddlesden–Popper-type H2[SrTa2O7] and H2[La2Ti3O10], and H1.8[(Sr0.8Bi0.2)Ta2O7] derived from an Aurivillius phase, Bi2Sr2Ta2O9, have been investigated by solid-state 1H nuclear magnetic resonance spectroscopy (NMR). Solid-state 1H NMR with a magic-angle spinning technique conducted at room temperature reveals that the mean electron densities around the 1H nuclei in these protonated forms are relatively low, and that they decrease in the following order: H1.8[(Sr0.8Bi0.2)Ta2O7]>H[LaNb2O7]>H2[SrTa2O7]>H[LaTa2O7]>H2[La2Ti3O10]. The temperature-dependent solid-state 1H broad-line NMR spectra measured at 140–400 K reveal a decrease in the signal width for all of these five samples upon heating due to motional narrowing. The NMR spectra of H[LaNb2O7] and H[LaTa2O7] are different from the other three protonated forms due to the weaker dipole–dipole interactions at low temperatures and lower mobility of the hydrogen atoms at high temperatures.
Here's one article with NMR. Anyone interested?
Local Environments and Dynamics of Hydrogen Stoms in Protonated Forms of Ion-Exchangeable Layered Perovskites Estimated by Solid-State 1H NMR.
S. Tani, Y. Komori, S. Hayashi, Y. Sugahara.
JSolidStateChem (2006) 179, 3357.
Abstract:
The local environments and dynamics of hydrogen atoms in five samples of protonated forms of ion-exchangeable layered perovskites, Dion–Jacobson-type H[LaNb2O7] and H[LaTa2O7], Ruddlesden–Popper-type H2[SrTa2O7] and H2[La2Ti3O10], and H1.8[(Sr0.8Bi0.2)Ta2O7] derived from an Aurivillius phase, Bi2Sr2Ta2O9, have been investigated by solid-state 1H nuclear magnetic resonance spectroscopy (NMR). Solid-state 1H NMR with a magic-angle spinning technique conducted at room temperature reveals that the mean electron densities around the 1H nuclei in these protonated forms are relatively low, and that they decrease in the following order: H1.8[(Sr0.8Bi0.2)Ta2O7]>H[LaNb2O7]>H2[SrTa2O7]>H[LaTa2O7]>H2[La2Ti3O10]. The temperature-dependent solid-state 1H broad-line NMR spectra measured at 140–400 K reveal a decrease in the signal width for all of these five samples upon heating due to motional narrowing. The NMR spectra of H[LaNb2O7] and H[LaTa2O7] are different from the other three protonated forms due to the weaker dipole–dipole interactions at low temperatures and lower mobility of the hydrogen atoms at high temperatures.
JPCB Update
It's been a while but here are some highlights from the past couple of months. This is only up to issue 43 more to come.
Interesting application ...
Generalized Two-Dimensional Correlation Analysis of NMR and Raman Spectra for Structural Evolution Characterizations of Silk Fibroin
Bing-Wen Hu, Ping Zhou, Isao Noda, and Qing-Xia Ruan
J.Phys.Chem.B (2006)110, 18046
Abstract:
Generalized two-dimensional (2D) correlation spectroscopy was used to characterize the structural evolution of silk fibroin as the pH changed from 6.8 to 4.8, demonstrating that the conformational transitions of silk fibroin are induced step by step as the pH decreases. 2D homo- and hetero-spectral correlation spectroscopy was used to establish the relationship between information extracted from NMR and Raman spectroscopy. This novel method reveals the structural evolution using two probes with different frequency scales (105-9 Hz for nuclear spin motion and 1012-14 Hz for molecular vibration motion), reflecting the different spatial scale sensitivity to the molecular conformational change. The transition order is identified as silk I state (helix dominant) silk I intermediate state silk II intermediate state silk II state (-sheet dominant), as the pH decreases. The results may rationalize the silkworm spinning process, which undergoes the conformational transition steadily from the soluble helix state to the insoluble -sheet state as the pH decreases from the posterior to anterior glands.
Hiyam
Low-Frequency Cooperative Dynamics in L-, D-, and DL-Alanine Crystals: A 13C and 15N Cross-Polarization Magic-Angle-Spinning NMR Study
Sabyasachi Sen, Ping Yu, Subhash H. Risbud, Reay Dick, and David Deamer
J.Phys.Chem.B (2006)110, 18058.
Abstract:
Knowledge of the dynamical changes in molecular configurations in various amino acid structures over a wide range of time scales is important since such changes may influence the structural transformations and the diverse biological functionalities of proteins. Using the temperature dependence of the rotating-frame NMR spin-lattice relaxation times T1 of protons as a probe, we have investigated the low-frequency (~60-100 kHz) dynamics in the crystal structures of L-, D-, and DL- alanine (C12H28O8N4) polymorphs. The proton relaxation times T1 were obtained from 13C 1H and 15N 1H cross-polarization magic-angle-spinning NMR experiments over a temperature range of 192-342 K. The data reveal that the time scales of these low-frequency dynamical processes are distinctly different from the localized, high-frequency rotational motion of methyl and amine groups. The strongly asymmetric T1 versus temperature curves and the subtle dynamical differences between the DL-alanine and the L- and D-enantiomorphs indicate that these low-frequency processes are cooperative in nature and are sensitive to molecular packing.
Joel
Direct Solid-State NMR Spectroscopic Evidence for the NH4AlF4 Crystalline Phase Derived from Zeolite HY Dealuminated with Ammonium Hexafluorosilicate
Hsien-Ming Kao and Pai-Ching Chang
J.Phys.Chem.B (2006)110, 19104.
Abstract:
Multinuclear 1H, 19F, and 27Al MAS (magic angle spinning) and corresponding 2D HETCOR (heteronuclear correlation) NMR spectroscopy, in combination with powder XRD measurements, provide the direct evidence for the NH4AlF4 crystalline phase, which was formed from zeolite HY dealuminated with an aqueous (NH4)2SiF6 solution at 80 C. The NH4AlF4 crystalline phase exhibits a characteristic second-order quadrupolar-induced 27Al NMR line shape spreading from 0 to -90 ppm (in a magnetic field of 11.7 T) and two 19F resonances at -151 and -166 ppm in the 19F NMR spectrum. An 27Al quadrupolar coupling constant (CQ) of 9.5 MHz and an asymmetry parameter () of 0.1 were identified, for the first time, for the NH4AlF4 crystalline phase observed. On the basis of the 19F{27Al} TRAPDOR (transfer population in double resonance) NMR results, the 19F resonances at -151 and -166 ppm are therefore assigned to 19F spins associated with the fluorines in the terminal Al-F and the bridging Al-F-Al groups, respectively.
Andy
Dynamics of Benzene Guest Inside a Self-Assembled Cylindrical Capsule: A Combined Solid-State 2H NMR and Molecular Dynamics Simulation Study
Alexandra R. Albunia, Carmine Gaeta, Placido Neri, Alfonso Grassi, and Giuseppe Milano
J.Phys.Chem.B (2006)110, 19207.
Abstract:
The reorientational dynamics of benzene-d6 molecules hosted into the cavity of a cavitand-based, self-assembled capsule was investigated by Molecular Dynamics (MD) simulations and temperature-dependent solid-state 2H NMR spectroscopy. MD simulations were preliminarily performed to assess the motional models of the guest molecules inside the capsules. An in-plane fast reorientation of the benzene guest around the C6 symmetry axis (B1 motion), characterized by correlation times of the order of picoseconds, was predicted with an activation barrier (~8 kJ/mol) very similar to that found for neat benzene in the liquid state. An out-of-plane reorientation corresponding to a nutation of the C6 symmetry axis in a cone angle of 39 (B2 motion, 373 K) with an activation barrier (~39 kJ/mol) definitely larger than that of liquid benzene was also anticipated. In the temperature range 293-373 K correlation times of the order of a nanosecond have been calculated and a transition from fast to slow regime in the 2H NMR scale has been predicted between 293 and 173 K. 2H NMR spectroscopic analysis, carried out in the temperature range 173-373 K on the solid capsules containing the perdeuterated guest (two benzene molecules/capsule), confirmed the occurrence of the B1 and B2 motions found in slow exchange in the 2H NMR time scale. Line shape simulation of the 2H NMR spectral lines permitted defining a cone angle value of 39 at 373 K and 35 at 173 K for the nutation axis. The T1 values measured for the 2H nuclei of the encapsulated aromatic guest gave correlation times and energetic barrier for the in-plane motion B1 in fine agreement with theoretical calculation. The experimental correlation time for B2 as well as the corresponding energetic barrier are in the same range found for B1. A molecular mechanism for the encapsulated guest accounting for the B1 and B2 motions was also provided.
Hiyam
15N MAS NMR Studies of Cph1 Phytochrome: Chromophore Dynamics and Intramolecular Signal Transduction
Thierry Rohmer, Holger Strauss, Jon Hughes, Huub de Groot, Wolfgang Gärtner, Peter Schmieder, and Jörg Matysik
J.Phys.Chem.B (2006)110, 20580.
Abstract:
Solid-state nuclear magnetic resonance (NMR) is applied for the first time to the photoreceptor phytochrome. The two stable states, Pr and Pfr, of the 59-kDa N-terminal module of the cyanobacterial phytochrome Cph1 from Synechocystis sp. PCC 6803 containing a uniformly 15N-labeled phycocyanobilin cofactor are explored by 15N cross-polarization (CP) magic-angle spinning (MAS) NMR. As recently shown by 15N solution-state NMR using chemical shifts [Strauss, H. M.; Hughes, J.; Schmieder, P. Biochemistry 2005, 44, 8244], all four nitrogens are protonated in both states. CP/MAS NMR provides two additional independent lines of evidence for the protonation of the nitrogens. Apparent loss of mobility during photoactivation, indicated by the decrease of line width, demonstrates strong tension of the entire chromophore in the Pfr state, which is in clear contrast to a more relaxed Pr state. The outer rings (A and D) of the chromophore are significantly affected by the phototransformation, as indicated by both change of chemical shift and line width. On the other hand, on the inner rings (B and C) only minor changes of chemical shifts are detected, providing evidence for a conserved environment during phototransformation. In a mechanical model, the phototransformation is understood in terms of rotations between the A-B and C-D methine bridges, allowing for intramolecular signal transduction to the protein surface by a unit composed of the central rings B and C and its tightly linked protein surroundings during the highly energetic Pfr state.
Andy
First-Principles Calculations within Periodic Boundary Conditions of the NMR Shielding Tensor for a Transition Metal Nucleus in a Solid State System: The Example of 51V in AlVO4
L. Truflandier, M. Paris, C. Payen, and F. Boucher
J.Phys.Chem.B (2006)110, 21403.
Abstract:
We present the first density functional theory based calculations of NMR shielding parameters for a transition metal nucleus using periodic boundary conditions. These calculations employ the gauge-including projected augmented-wave pseudopotential approach. The quality of this method is discussed by comparing experimental and calculated chemical shift tensor eigenvalues for the quadrupolar 51V nucleus in the diamagnetic solid-state compound AlVO4. Furthermore, the combination of shielding tensor with fast and accurate projector augmented-wave electric field gradient tensor calculations allows us to determine the relative orientation of these two tensors.
Interesting application ...
Generalized Two-Dimensional Correlation Analysis of NMR and Raman Spectra for Structural Evolution Characterizations of Silk Fibroin
Bing-Wen Hu, Ping Zhou, Isao Noda, and Qing-Xia Ruan
J.Phys.Chem.B (2006)110, 18046
Abstract:
Generalized two-dimensional (2D) correlation spectroscopy was used to characterize the structural evolution of silk fibroin as the pH changed from 6.8 to 4.8, demonstrating that the conformational transitions of silk fibroin are induced step by step as the pH decreases. 2D homo- and hetero-spectral correlation spectroscopy was used to establish the relationship between information extracted from NMR and Raman spectroscopy. This novel method reveals the structural evolution using two probes with different frequency scales (105-9 Hz for nuclear spin motion and 1012-14 Hz for molecular vibration motion), reflecting the different spatial scale sensitivity to the molecular conformational change. The transition order is identified as silk I state (helix dominant) silk I intermediate state silk II intermediate state silk II state (-sheet dominant), as the pH decreases. The results may rationalize the silkworm spinning process, which undergoes the conformational transition steadily from the soluble helix state to the insoluble -sheet state as the pH decreases from the posterior to anterior glands.
Hiyam
Low-Frequency Cooperative Dynamics in L-, D-, and DL-Alanine Crystals: A 13C and 15N Cross-Polarization Magic-Angle-Spinning NMR Study
Sabyasachi Sen, Ping Yu, Subhash H. Risbud, Reay Dick, and David Deamer
J.Phys.Chem.B (2006)110, 18058.
Abstract:
Knowledge of the dynamical changes in molecular configurations in various amino acid structures over a wide range of time scales is important since such changes may influence the structural transformations and the diverse biological functionalities of proteins. Using the temperature dependence of the rotating-frame NMR spin-lattice relaxation times T1 of protons as a probe, we have investigated the low-frequency (~60-100 kHz) dynamics in the crystal structures of L-, D-, and DL- alanine (C12H28O8N4) polymorphs. The proton relaxation times T1 were obtained from 13C 1H and 15N 1H cross-polarization magic-angle-spinning NMR experiments over a temperature range of 192-342 K. The data reveal that the time scales of these low-frequency dynamical processes are distinctly different from the localized, high-frequency rotational motion of methyl and amine groups. The strongly asymmetric T1 versus temperature curves and the subtle dynamical differences between the DL-alanine and the L- and D-enantiomorphs indicate that these low-frequency processes are cooperative in nature and are sensitive to molecular packing.
Joel
Direct Solid-State NMR Spectroscopic Evidence for the NH4AlF4 Crystalline Phase Derived from Zeolite HY Dealuminated with Ammonium Hexafluorosilicate
Hsien-Ming Kao and Pai-Ching Chang
J.Phys.Chem.B (2006)110, 19104.
Abstract:
Multinuclear 1H, 19F, and 27Al MAS (magic angle spinning) and corresponding 2D HETCOR (heteronuclear correlation) NMR spectroscopy, in combination with powder XRD measurements, provide the direct evidence for the NH4AlF4 crystalline phase, which was formed from zeolite HY dealuminated with an aqueous (NH4)2SiF6 solution at 80 C. The NH4AlF4 crystalline phase exhibits a characteristic second-order quadrupolar-induced 27Al NMR line shape spreading from 0 to -90 ppm (in a magnetic field of 11.7 T) and two 19F resonances at -151 and -166 ppm in the 19F NMR spectrum. An 27Al quadrupolar coupling constant (CQ) of 9.5 MHz and an asymmetry parameter () of 0.1 were identified, for the first time, for the NH4AlF4 crystalline phase observed. On the basis of the 19F{27Al} TRAPDOR (transfer population in double resonance) NMR results, the 19F resonances at -151 and -166 ppm are therefore assigned to 19F spins associated with the fluorines in the terminal Al-F and the bridging Al-F-Al groups, respectively.
Andy
Dynamics of Benzene Guest Inside a Self-Assembled Cylindrical Capsule: A Combined Solid-State 2H NMR and Molecular Dynamics Simulation Study
Alexandra R. Albunia, Carmine Gaeta, Placido Neri, Alfonso Grassi, and Giuseppe Milano
J.Phys.Chem.B (2006)110, 19207.
Abstract:
The reorientational dynamics of benzene-d6 molecules hosted into the cavity of a cavitand-based, self-assembled capsule was investigated by Molecular Dynamics (MD) simulations and temperature-dependent solid-state 2H NMR spectroscopy. MD simulations were preliminarily performed to assess the motional models of the guest molecules inside the capsules. An in-plane fast reorientation of the benzene guest around the C6 symmetry axis (B1 motion), characterized by correlation times of the order of picoseconds, was predicted with an activation barrier (~8 kJ/mol) very similar to that found for neat benzene in the liquid state. An out-of-plane reorientation corresponding to a nutation of the C6 symmetry axis in a cone angle of 39 (B2 motion, 373 K) with an activation barrier (~39 kJ/mol) definitely larger than that of liquid benzene was also anticipated. In the temperature range 293-373 K correlation times of the order of a nanosecond have been calculated and a transition from fast to slow regime in the 2H NMR scale has been predicted between 293 and 173 K. 2H NMR spectroscopic analysis, carried out in the temperature range 173-373 K on the solid capsules containing the perdeuterated guest (two benzene molecules/capsule), confirmed the occurrence of the B1 and B2 motions found in slow exchange in the 2H NMR time scale. Line shape simulation of the 2H NMR spectral lines permitted defining a cone angle value of 39 at 373 K and 35 at 173 K for the nutation axis. The T1 values measured for the 2H nuclei of the encapsulated aromatic guest gave correlation times and energetic barrier for the in-plane motion B1 in fine agreement with theoretical calculation. The experimental correlation time for B2 as well as the corresponding energetic barrier are in the same range found for B1. A molecular mechanism for the encapsulated guest accounting for the B1 and B2 motions was also provided.
Hiyam
15N MAS NMR Studies of Cph1 Phytochrome: Chromophore Dynamics and Intramolecular Signal Transduction
Thierry Rohmer, Holger Strauss, Jon Hughes, Huub de Groot, Wolfgang Gärtner, Peter Schmieder, and Jörg Matysik
J.Phys.Chem.B (2006)110, 20580.
Abstract:
Solid-state nuclear magnetic resonance (NMR) is applied for the first time to the photoreceptor phytochrome. The two stable states, Pr and Pfr, of the 59-kDa N-terminal module of the cyanobacterial phytochrome Cph1 from Synechocystis sp. PCC 6803 containing a uniformly 15N-labeled phycocyanobilin cofactor are explored by 15N cross-polarization (CP) magic-angle spinning (MAS) NMR. As recently shown by 15N solution-state NMR using chemical shifts [Strauss, H. M.; Hughes, J.; Schmieder, P. Biochemistry 2005, 44, 8244], all four nitrogens are protonated in both states. CP/MAS NMR provides two additional independent lines of evidence for the protonation of the nitrogens. Apparent loss of mobility during photoactivation, indicated by the decrease of line width, demonstrates strong tension of the entire chromophore in the Pfr state, which is in clear contrast to a more relaxed Pr state. The outer rings (A and D) of the chromophore are significantly affected by the phototransformation, as indicated by both change of chemical shift and line width. On the other hand, on the inner rings (B and C) only minor changes of chemical shifts are detected, providing evidence for a conserved environment during phototransformation. In a mechanical model, the phototransformation is understood in terms of rotations between the A-B and C-D methine bridges, allowing for intramolecular signal transduction to the protein surface by a unit composed of the central rings B and C and its tightly linked protein surroundings during the highly energetic Pfr state.
Andy
First-Principles Calculations within Periodic Boundary Conditions of the NMR Shielding Tensor for a Transition Metal Nucleus in a Solid State System: The Example of 51V in AlVO4
L. Truflandier, M. Paris, C. Payen, and F. Boucher
J.Phys.Chem.B (2006)110, 21403.
Abstract:
We present the first density functional theory based calculations of NMR shielding parameters for a transition metal nucleus using periodic boundary conditions. These calculations employ the gauge-including projected augmented-wave pseudopotential approach. The quality of this method is discussed by comparing experimental and calculated chemical shift tensor eigenvalues for the quadrupolar 51V nucleus in the diamagnetic solid-state compound AlVO4. Furthermore, the combination of shielding tensor with fast and accurate projector augmented-wave electric field gradient tensor calculations allows us to determine the relative orientation of these two tensors.
Wednesday, September 27, 2006
Prog NMR: Silver NMR review article - Glenn Penner
Progress in Nuclear Magnetic Resonance Spectroscopy
Volume 49, Issue 2 , 30 September 2006, Pages 151-167
Silver NMR spectroscopy
Glenn H. Penner and Xiaolong Liu
Department of Chemistry, University of Guelph, Guelph, Ont., Canada N1G 2W1
Keywords: NMR spectroscopy; Solid state NMR; Silver
Volume 49, Issue 2 , 30 September 2006, Pages 151-167
Silver NMR spectroscopy
Glenn H. Penner and Xiaolong Liu
Department of Chemistry, University of Guelph, Guelph, Ont., Canada N1G 2W1
Keywords: NMR spectroscopy; Solid state NMR; Silver
Friday, September 01, 2006
JMR: Bodenhausen, indirect detection of 14N via 1H (HMQC type experiment)
Journal of Magnetic Resonance
Vol: 182 Issue: 1, September, 2006
Communication
Indirect detection of nitrogen-14 in solids via protons by nuclear magnetic resonance spectroscopy
Simone Cavadini a, Sasa Antonijevic a, , Email Address, Adonis Lupulescu a, Geoffrey Bodenhausen a, b
a Laboratoire de Résonance Magnétique Biomoléculaire, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, Batochime, CH-1015 Lausanne, Switzerland
b Département de Chimie, associé au CNRS, Ecole Normale Supérieure, 24 rue Lhomond 75231, Paris Cedex 05, France
Abstract
This Communication describes the indirect detection of 14 N nuclei (spin I = 1) in solids by nuclear magnetic resonance (NMR) spectroscopy. The two-dimensional correlation method used here is closely related to the heteronuclear multiple quantum correlation (HMQC) experiment introduced in 1979 to study molecules in liquids, which has recently been used to study solids spinning at the magic angle. The difference is that the coherence transfer from neighboring 1 H nuclei to 14 N is achieved via a combination of J couplings and residual dipolar splittings (RDS). Projections of the two-dimensional correlation spectra onto the 14 N dimension yield powder patterns which reflect the 14 N quadrupolar interaction. In contrast to the indirect detection of 14 N via 13 C nuclei that was recently demonstrated [Gan, J. Am. Chem. Soc. 128 (2006) 6040; Cavadini et. al., J. Am. Chem. Soc., 128 (2006) 7706], this approach may benefit from enhanced sensitivity, and does not require isotopic enrichment in 13 C, although the 1 H line-widths may have to be reduced upon selective deuteration.
Vol: 182 Issue: 1, September, 2006
Communication
Indirect detection of nitrogen-14 in solids via protons by nuclear magnetic resonance spectroscopy
Simone Cavadini a, Sasa Antonijevic a, , Email Address, Adonis Lupulescu a, Geoffrey Bodenhausen a, b
a Laboratoire de Résonance Magnétique Biomoléculaire, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne, Batochime, CH-1015 Lausanne, Switzerland
b Département de Chimie, associé au CNRS, Ecole Normale Supérieure, 24 rue Lhomond 75231, Paris Cedex 05, France
Abstract
This Communication describes the indirect detection of 14 N nuclei (spin I = 1) in solids by nuclear magnetic resonance (NMR) spectroscopy. The two-dimensional correlation method used here is closely related to the heteronuclear multiple quantum correlation (HMQC) experiment introduced in 1979 to study molecules in liquids, which has recently been used to study solids spinning at the magic angle. The difference is that the coherence transfer from neighboring 1 H nuclei to 14 N is achieved via a combination of J couplings and residual dipolar splittings (RDS). Projections of the two-dimensional correlation spectra onto the 14 N dimension yield powder patterns which reflect the 14 N quadrupolar interaction. In contrast to the indirect detection of 14 N via 13 C nuclei that was recently demonstrated [Gan, J. Am. Chem. Soc. 128 (2006) 6040; Cavadini et. al., J. Am. Chem. Soc., 128 (2006) 7706], this approach may benefit from enhanced sensitivity, and does not require isotopic enrichment in 13 C, although the 1 H line-widths may have to be reduced upon selective deuteration.
Organometallics: SSNMR of ferrocene derivatives
Organometallics, ASAP Article 10.1021/om060468w S0276-7333(06)00468-7
Web Release Date: August 18, 2006
A Solid-Gas Route to Polymorph Conversion in Crystalline [FeII(5-C5H4COOH)2]. A Diffraction and Solid-State NMR Study
Dario Braga, Fabrizia Grepioni,* and Marco Polito*
Dipartimento di Chimica G Ciamician, Università di Bologna, 40126 Bologna, Italy
Michele R. Chierotti, Silvano Ellena, and Roberto Gobetto*
Dipartimento di Chimica IFM, Università di Torino, 101256 Torino, Italy
Abstract:
Crystalline form I (monoclinic) and form II (triclinic) of ferrocene dicarboxylic acid [Fe(5-C5H4COOH)2] have been employed in solid-gas reactions at room temperature with the gaseous bases NH3, NH2(CH3), and NH(CH3)2. The two crystal forms behave in exactly the same way in the solid-gas reaction, generating the same products, identified as the anhydrous crystalline salts [NH4]2[Fe(5-C5H4COO)2] (1), [NH3CH3]2[Fe(5-C5H4COO)2] (2), and [NH2(CH3)2]2[Fe(5-C5H4COO)2] (3). Interestingly though, all these crystals revert via vapor release exclusively to the metastable crystalline form I. Starting materials and products have been investigated by single-crystal and powder diffraction and by 13C, 15N CPMAS and 1H MAS methods.
Web Release Date: August 18, 2006
A Solid-Gas Route to Polymorph Conversion in Crystalline [FeII(5-C5H4COOH)2]. A Diffraction and Solid-State NMR Study
Dario Braga, Fabrizia Grepioni,* and Marco Polito*
Dipartimento di Chimica G Ciamician, Università di Bologna, 40126 Bologna, Italy
Michele R. Chierotti, Silvano Ellena, and Roberto Gobetto*
Dipartimento di Chimica IFM, Università di Torino, 101256 Torino, Italy
Abstract:
Crystalline form I (monoclinic) and form II (triclinic) of ferrocene dicarboxylic acid [Fe(5-C5H4COOH)2] have been employed in solid-gas reactions at room temperature with the gaseous bases NH3, NH2(CH3), and NH(CH3)2. The two crystal forms behave in exactly the same way in the solid-gas reaction, generating the same products, identified as the anhydrous crystalline salts [NH4]2[Fe(5-C5H4COO)2] (1), [NH3CH3]2[Fe(5-C5H4COO)2] (2), and [NH2(CH3)2]2[Fe(5-C5H4COO)2] (3). Interestingly though, all these crystals revert via vapor release exclusively to the metastable crystalline form I. Starting materials and products have been investigated by single-crystal and powder diffraction and by 13C, 15N CPMAS and 1H MAS methods.
JACS: Fyfe & Brouwer: Structures of Zeolite Host-Guest Systems by NMR
J. Am. Chem. Soc., ASAP Article 10.1021/ja060744y S0002-7863(06)00744-X
Web Release Date: August 17, 2006
Optimization, Standardization, and Testing of a New NMR Method for the Determination of Zeolite Host-Organic Guest Crystal Structures
Colin A. Fyfe* and Darren H. Brouwer
Contribution from the Department of Chemistry, University of British Columbia, R300, 6174 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z3
Abstract:
An optimized and automated protocol for determining the location of guest sorbate molecules in highly siliceous zeolites from 29Si INADEQUATE and 1H/29Si cross polarization (CP) magic-angle spinning (MAS) NMR experiments is described. With the peaks in the 29Si MAS NMR spectrum assigned to the unique Si sites in the zeolite framework by a 2D 29Si INADEQUATE experiment, the location of the sorbate molecule is found by systematically searching for sorbate locations for which the measured rates of 1H/29Si cross polarization of the different Si sites correlate linearly with 1H/29Si second moments calculated from H-Si distances. Due to the 1H/29Si cross polarization being in the "slow CP regime" for many zeolite-sorbate complexes, it is proposed that the CP rate constants are best measured by 1H/29Si cross polarization drain experiments, if possible, to avoid complications that may arise from fast 1H and 29Si T1 relaxations. An algorithm for determining the sorbate molecule location is described in detail. A number of ways to effectively summarize and display the large number of solutions which typically result from a prediction of the structure from the CP MAS NMR data are presented, including estimates of the errors involved in the structure determinations. As a working example throughout this paper, the structure of the low loaded p-dichlorobenzene/ZSM-5 complex is determined under different conditions from solid-state 1H/29Si CP MAS NMR data, and the solutions are shown to be in excellent agreement with the known single-crystal X-ray diffraction structure. This structure determination approach is shown to be quite insensitive to the use of relative rate constants rather than absolute values, to the detailed structure of the zeolite framework, and relatively insensitive to temperature and motions.
Web Release Date: August 17, 2006
Optimization, Standardization, and Testing of a New NMR Method for the Determination of Zeolite Host-Organic Guest Crystal Structures
Colin A. Fyfe* and Darren H. Brouwer
Contribution from the Department of Chemistry, University of British Columbia, R300, 6174 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z3
Abstract:
An optimized and automated protocol for determining the location of guest sorbate molecules in highly siliceous zeolites from 29Si INADEQUATE and 1H/29Si cross polarization (CP) magic-angle spinning (MAS) NMR experiments is described. With the peaks in the 29Si MAS NMR spectrum assigned to the unique Si sites in the zeolite framework by a 2D 29Si INADEQUATE experiment, the location of the sorbate molecule is found by systematically searching for sorbate locations for which the measured rates of 1H/29Si cross polarization of the different Si sites correlate linearly with 1H/29Si second moments calculated from H-Si distances. Due to the 1H/29Si cross polarization being in the "slow CP regime" for many zeolite-sorbate complexes, it is proposed that the CP rate constants are best measured by 1H/29Si cross polarization drain experiments, if possible, to avoid complications that may arise from fast 1H and 29Si T1 relaxations. An algorithm for determining the sorbate molecule location is described in detail. A number of ways to effectively summarize and display the large number of solutions which typically result from a prediction of the structure from the CP MAS NMR data are presented, including estimates of the errors involved in the structure determinations. As a working example throughout this paper, the structure of the low loaded p-dichlorobenzene/ZSM-5 complex is determined under different conditions from solid-state 1H/29Si CP MAS NMR data, and the solutions are shown to be in excellent agreement with the known single-crystal X-ray diffraction structure. This structure determination approach is shown to be quite insensitive to the use of relative rate constants rather than absolute values, to the detailed structure of the zeolite framework, and relatively insensitive to temperature and motions.
Prog. in NMR: platinum anti-cancer drugs and 195Pt NMR - Review article
Review article
Progress in Nuclear Magnetic Resonance Spectroscopy
Volume 49, Issue 1 , 15 August 2006, Pages 65-98
Insights into the mechanism of action of platinum anticancer drugs from multinuclear NMR spectroscopy
Susan J. Berners-Price, Luca Ronconi and Peter J. Sadler
School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, Perth, WA 6009, Australia
School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
Keywords: NMR; Platinum drugs; 195Pt NMR; 15N NMR; [1H,15N] NMR; Proteins; Glutathione; DNA; Aquation; Kinetics
Progress in Nuclear Magnetic Resonance Spectroscopy
Volume 49, Issue 1 , 15 August 2006, Pages 65-98
Insights into the mechanism of action of platinum anticancer drugs from multinuclear NMR spectroscopy
Susan J. Berners-Price, Luca Ronconi and Peter J. Sadler
School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, Perth, WA 6009, Australia
School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
Keywords: NMR; Platinum drugs; 195Pt NMR; 15N NMR; [1H,15N] NMR; Proteins; Glutathione; DNA; Aquation; Kinetics
Prog. in NMR: Paramagnetic relaxitivity -Review article
Review article
Progress in Nuclear Magnetic Resonance Spectroscopy
Volume 49, Issue 1 , 15 August 2006, Pages 45-64
Relaxivity in paramagnetic systems: Theory and mechanisms
Lothar Helm
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-BCH, CH-1015 Lausanne, Switzerland
Keywords: Paramagnetic NMR relaxation; EPR relaxation; Zero-field splitting; MRI contrast agents
Progress in Nuclear Magnetic Resonance Spectroscopy
Volume 49, Issue 1 , 15 August 2006, Pages 45-64
Relaxivity in paramagnetic systems: Theory and mechanisms
Lothar Helm
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, EPFL-BCH, CH-1015 Lausanne, Switzerland
Keywords: Paramagnetic NMR relaxation; EPR relaxation; Zero-field splitting; MRI contrast agents
Sunday, August 27, 2006
JPCB Update
19F Single-Quantum and 19F-33S Heteronuclear Multiple-Quantum Coherence NMR of SF6 in Thermotropic Nemtogens and in the Gas Phase.
H. Tervonen, J. Saunavaara, L.P. Ingman, and J. Jokisaari
J.Phys.Chem.B(2006)110,16232.
Abstract:
19F single-quantum (SQC) and 19F-33S heteronuclear multiple-quantum coherence (HMQC) NMR spectroscopy of sulfur hexafluoride (SF6) dissolved in thermotropic liquid crystals (TLCs) were used to investigate the properties of TLCs. On one hand, environmental effects on the NMR parameters of SF6, 19F nuclear shielding, 19F-33S spin-spin coupling, secondary isotope effects of sulfur on 19F shielding, and the self-diffusion coefficient in the direction of the external magnetic field were studied as well. The temperature dependence of the 19F shielding of SF6 in TLCs was modeled with a function that takes into account the properties of both TLC and SF6. It appears that the TLC environment deforms the electronic system of SF6 so that the 19F shielding tensor becomes slightly anisotropic, with the anisotropy being from -0.5 to -1.4 ppm, depending upon the TLC solvent. On the contrary, no sign of residual dipolar coupling between 19F and 33S was found, meaning that the so-called deformational effects, which arise from the interaction between vibrational and reorientational motions of the molecule, on the geometry of the molecule are insignificant. Diffusion activation energies, Ea, were determined from the temperature dependence of the self-diffusion coefficients. In each TLC, Ea increases when moving from an isotropic phase to a nematic phase. The spin-spin coupling constant, J(19F,33S), increases by ca. 10 Hz when moving from the gas phase to TLC solutions. The secondary isotope shifts of 19F shielding are practically independent of TLC solvent and temperature. For the first time, 19F-33S heteronuclear multiple-quantum NMR spectra were recorded for SF6 in the gas phase and in a liquid-crystalline solution.
Atomistic Origin of Germanate Anomaly in GeO2 and Na-Germanate Glasses: Insights from Two-Dimensional; 17O NMR and Quantum Chemical Calculations.
S.K. Lee and B.H. Lee
J.Phys.Chem.B (2006)110, 16408.
Abstract:
The prominent problem in archetypal germanate glasses is the germanate anomaly where the density exhibits maxima at 15-20 mol % of the alkali oxide content. Here we report 17O two-dimensional NMR spectra for GeO2 and Na-germanate glasses where the presence of both bridging oxygen linking [4]Ge and highly coordinated Ge ([5,6]Ge-O-[4]Ge) and nonbridging oxygen, and an increase in topological disorder are demonstrated at the density maximum, manifesting atomic origins of the anomaly. These densification mechanisms in germanate glasses with Na content are remarkably similar to densification in v-B2O3 with pressure.
Thermally Stable Amorphous Mesoporous Alumniophosphates with Controllable P/Al Ratio: Synthesis, Characterization and Catalytic Performance for Selective O-Methylation of Catechol.
G. Liu, Z. Wang, M. Jia, X. Zou, X. Zhu, W. Zhang, and D Jiang
J.Phys.Chem.B (2006)110, 16953.
Abstract:
Amorphous mesoporous aluminophosphates (AlPO) with P/Al molar ratio in the range 0.8-1.15 are synthesized by using the citric acid (CA) route and are systematically characterized using N2-adsorption, XRD, SEM, solid-state CP-MAS NMR, FT-IR, TG-DTA, CO2-TPD, and NH3-TPD. The characterization studies show that the change in P/Al ratio could affect the structure, texture, thermal stability, and surface acid-base properties of AlPO. Samples with a relatively low P/Al ratio (1.0) exhibit uniform amorphous mesoporous character and high thermal stability (up to 1173 K). Partial crystallization of the AlPO framework easily occurred on the sample with higher P/Al ratio (1.1), thus leading to significant decrease of surface area and formation of particle pile mesopores. Both weak acid and weak base sites are observed over AlPO materials, and the amounts of acid-base sites can be effectively controlled by adjusting the P/Al ratio. The presence of suitable interaction between citric acid and AlPO framework is critical for the formation of mesoporous structures. Both CA and PO4 units are considered to be ligands to coordinate with aluminum ions, forming relative uniform complexes (such as CA-Al-PO4) in the as-synthesized AlPO materials. The mesoporous structure of AlPO materials is obtained after the rapid decomposition of citric acid. Vapor phase selective O-methylation of catechol with methanol reaction is carried out to investigate the catalytic performances of AlPO materials with different P/Al ratios. Among them, AlP1.1O shows the highest activity (88.4% conversion of catechol) and the highest yield of guaiacol (74.3%). The presence of suitable weak acid-base pairs may play an important role on the title reaction.
Selective NMR Measurements of Homonuclear Scalar Couplings in Isotropically Enriched Solids.
S. Cadars, A. Lesarge, N. Hedin, B.F. Chmelka, and L. Emsley
J.Phys.Chem.B (2006)110, 16982.
Abstract:
Scalar (J) couplings in solid-state NMR spectroscopy are sensitive to covalent through-bond interactions that make them informative structural probes for a wide range of complex materials. Until now, however, they have been generally unsuitable for use in isotopically enriched solids, such as proteins or many inorganic solids, because of the complications presented by multiple coupled but nonisolated spins. Such difficulties are overcome by incorporating a z-filter that results in a robust method for measuring pure J-coupling modulations between selected pairs of nuclei in an isotopically enriched spin system. The reliability of the new experimental approach is established by using numerical simulations and tested on fully 13C-labeled polycrystalline L-alanine. It is furthermore shown to be applicable to partially enriched systems, when used in combination with a selective double-quantum (DQ) filter, as demonstrated for the measurement of 2J(29Si-O-29Si) couplings in a 50% 29Si-enriched surfactant-templated layered silicate lacking long-range 3D crystallinity. J-coupling constants are obtained with sufficient accuracy to distinguish between different 29Si-O-29Si pairs, shedding insight on the local structure of the silicate framework. The new experiment is appropriate for fully or partially enriched liquid or solid samples.
H. Tervonen, J. Saunavaara, L.P. Ingman, and J. Jokisaari
J.Phys.Chem.B(2006)110,16232.
Abstract:
19F single-quantum (SQC) and 19F-33S heteronuclear multiple-quantum coherence (HMQC) NMR spectroscopy of sulfur hexafluoride (SF6) dissolved in thermotropic liquid crystals (TLCs) were used to investigate the properties of TLCs. On one hand, environmental effects on the NMR parameters of SF6, 19F nuclear shielding, 19F-33S spin-spin coupling, secondary isotope effects of sulfur on 19F shielding, and the self-diffusion coefficient in the direction of the external magnetic field were studied as well. The temperature dependence of the 19F shielding of SF6 in TLCs was modeled with a function that takes into account the properties of both TLC and SF6. It appears that the TLC environment deforms the electronic system of SF6 so that the 19F shielding tensor becomes slightly anisotropic, with the anisotropy being from -0.5 to -1.4 ppm, depending upon the TLC solvent. On the contrary, no sign of residual dipolar coupling between 19F and 33S was found, meaning that the so-called deformational effects, which arise from the interaction between vibrational and reorientational motions of the molecule, on the geometry of the molecule are insignificant. Diffusion activation energies, Ea, were determined from the temperature dependence of the self-diffusion coefficients. In each TLC, Ea increases when moving from an isotropic phase to a nematic phase. The spin-spin coupling constant, J(19F,33S), increases by ca. 10 Hz when moving from the gas phase to TLC solutions. The secondary isotope shifts of 19F shielding are practically independent of TLC solvent and temperature. For the first time, 19F-33S heteronuclear multiple-quantum NMR spectra were recorded for SF6 in the gas phase and in a liquid-crystalline solution.
Atomistic Origin of Germanate Anomaly in GeO2 and Na-Germanate Glasses: Insights from Two-Dimensional; 17O NMR and Quantum Chemical Calculations.
S.K. Lee and B.H. Lee
J.Phys.Chem.B (2006)110, 16408.
Abstract:
The prominent problem in archetypal germanate glasses is the germanate anomaly where the density exhibits maxima at 15-20 mol % of the alkali oxide content. Here we report 17O two-dimensional NMR spectra for GeO2 and Na-germanate glasses where the presence of both bridging oxygen linking [4]Ge and highly coordinated Ge ([5,6]Ge-O-[4]Ge) and nonbridging oxygen, and an increase in topological disorder are demonstrated at the density maximum, manifesting atomic origins of the anomaly. These densification mechanisms in germanate glasses with Na content are remarkably similar to densification in v-B2O3 with pressure.
Thermally Stable Amorphous Mesoporous Alumniophosphates with Controllable P/Al Ratio: Synthesis, Characterization and Catalytic Performance for Selective O-Methylation of Catechol.
G. Liu, Z. Wang, M. Jia, X. Zou, X. Zhu, W. Zhang, and D Jiang
J.Phys.Chem.B (2006)110, 16953.
Abstract:
Amorphous mesoporous aluminophosphates (AlPO) with P/Al molar ratio in the range 0.8-1.15 are synthesized by using the citric acid (CA) route and are systematically characterized using N2-adsorption, XRD, SEM, solid-state CP-MAS NMR, FT-IR, TG-DTA, CO2-TPD, and NH3-TPD. The characterization studies show that the change in P/Al ratio could affect the structure, texture, thermal stability, and surface acid-base properties of AlPO. Samples with a relatively low P/Al ratio (1.0) exhibit uniform amorphous mesoporous character and high thermal stability (up to 1173 K). Partial crystallization of the AlPO framework easily occurred on the sample with higher P/Al ratio (1.1), thus leading to significant decrease of surface area and formation of particle pile mesopores. Both weak acid and weak base sites are observed over AlPO materials, and the amounts of acid-base sites can be effectively controlled by adjusting the P/Al ratio. The presence of suitable interaction between citric acid and AlPO framework is critical for the formation of mesoporous structures. Both CA and PO4 units are considered to be ligands to coordinate with aluminum ions, forming relative uniform complexes (such as CA-Al-PO4) in the as-synthesized AlPO materials. The mesoporous structure of AlPO materials is obtained after the rapid decomposition of citric acid. Vapor phase selective O-methylation of catechol with methanol reaction is carried out to investigate the catalytic performances of AlPO materials with different P/Al ratios. Among them, AlP1.1O shows the highest activity (88.4% conversion of catechol) and the highest yield of guaiacol (74.3%). The presence of suitable weak acid-base pairs may play an important role on the title reaction.
Selective NMR Measurements of Homonuclear Scalar Couplings in Isotropically Enriched Solids.
S. Cadars, A. Lesarge, N. Hedin, B.F. Chmelka, and L. Emsley
J.Phys.Chem.B (2006)110, 16982.
Abstract:
Scalar (J) couplings in solid-state NMR spectroscopy are sensitive to covalent through-bond interactions that make them informative structural probes for a wide range of complex materials. Until now, however, they have been generally unsuitable for use in isotopically enriched solids, such as proteins or many inorganic solids, because of the complications presented by multiple coupled but nonisolated spins. Such difficulties are overcome by incorporating a z-filter that results in a robust method for measuring pure J-coupling modulations between selected pairs of nuclei in an isotopically enriched spin system. The reliability of the new experimental approach is established by using numerical simulations and tested on fully 13C-labeled polycrystalline L-alanine. It is furthermore shown to be applicable to partially enriched systems, when used in combination with a selective double-quantum (DQ) filter, as demonstrated for the measurement of 2J(29Si-O-29Si) couplings in a 50% 29Si-enriched surfactant-templated layered silicate lacking long-range 3D crystallinity. J-coupling constants are obtained with sufficient accuracy to distinguish between different 29Si-O-29Si pairs, shedding insight on the local structure of the silicate framework. The new experiment is appropriate for fully or partially enriched liquid or solid samples.
Sunday, August 20, 2006
Cross polarization from spins I=1/2 to spins S=1 in nuclear magnetic resonance with magic angle sample spinning
The Journal of Chemical Physics, 21 May 2006J. Chem. Phys. 124, 194311
Karthik Gopalakrishnan, Geoffrey Bodenhausen
Spin locking of the nuclear magnetization of a spin with S=1 such as deuterium in the presence of a radio-frequency field under magic angle spinning (MAS) is described in terms of adiabatic modulations of the energy levels. In a brief initial period, part of the initial density operator nutates about the Hamiltonian and is dephased. The remaining spin-locked state undergoes persistent oscillatory transfer processes between various coherences with a periodicity given by the rotation of the sample. While all crystallites in the powder undergo such periodic transfer processes, the phases of the oscillations depend on the angle of the crystallites. The angle is the azimuthal angle defining the orientation of the unique axis of the quadrupolar interaction tensor in a rotor-fixed frame. The theory is extended to describe cross-polarization between spins S=1 and I=1/2 under MAS. There are four distinct Hartmann-Hahn matching conditions that correspond to four zero-quantum matching conditions, all of which are shifted and broadened compared to their spin S=1/2 counterparts. These matching conditions are further split into a family of sideband conditions separated by the spinning frequency. The theory allows the calculation of both shifts and broadening factors of the matching conditions, as verified by simulations and experiments.
Karthik Gopalakrishnan, Geoffrey Bodenhausen
Spin locking of the nuclear magnetization of a spin with S=1 such as deuterium in the presence of a radio-frequency field under magic angle spinning (MAS) is described in terms of adiabatic modulations of the energy levels. In a brief initial period, part of the initial density operator nutates about the Hamiltonian and is dephased. The remaining spin-locked state undergoes persistent oscillatory transfer processes between various coherences with a periodicity given by the rotation of the sample. While all crystallites in the powder undergo such periodic transfer processes, the phases of the oscillations depend on the angle of the crystallites. The angle is the azimuthal angle defining the orientation of the unique axis of the quadrupolar interaction tensor in a rotor-fixed frame. The theory is extended to describe cross-polarization between spins S=1 and I=1/2 under MAS. There are four distinct Hartmann-Hahn matching conditions that correspond to four zero-quantum matching conditions, all of which are shifted and broadened compared to their spin S=1/2 counterparts. These matching conditions are further split into a family of sideband conditions separated by the spinning frequency. The theory allows the calculation of both shifts and broadening factors of the matching conditions, as verified by simulations and experiments.
Frequency-selective homonuclear dipolar recoupling in solid state NMR
The Journal of Chemical Physics, 21 May 2006J. Chem. Phys. 124, 194303
Anant K. Paravastu and Robert Tycko
We introduce a new approach to frequency-selective homonuclear dipolar recoupling in solid state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS). This approach, to which we give the acronym SEASHORE, employs alternating periods of double-quantum recoupling and chemical shift evolution to produce phase modulations of the recoupled dipole-dipole interactions that average out undesired couplings, leaving only dipole-dipole couplings between nuclear spins with a selected pair of NMR frequencies. In principle, SEASHORE is applicable to systems with arbitrary coupling strengths and arbitrary sets of NMR frequencies. Arbitrary MAS frequencies are also possible, subject only to restrictions imposed by the pulse sequence chosen for double-quantum recoupling. We demonstrate the efficacy of SEASHORE in experimental 13C NMR measurements of frequency-selective polarization transfer in uniformly 15N, 13C-labeled L-valine powder and frequency-selective intermolecular polarization transfer in amyloid fibrils formed by a synthetic decapeptide containing uniformly 15N, 13C-labeled residues.
Anant K. Paravastu and Robert Tycko
We introduce a new approach to frequency-selective homonuclear dipolar recoupling in solid state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS). This approach, to which we give the acronym SEASHORE, employs alternating periods of double-quantum recoupling and chemical shift evolution to produce phase modulations of the recoupled dipole-dipole interactions that average out undesired couplings, leaving only dipole-dipole couplings between nuclear spins with a selected pair of NMR frequencies. In principle, SEASHORE is applicable to systems with arbitrary coupling strengths and arbitrary sets of NMR frequencies. Arbitrary MAS frequencies are also possible, subject only to restrictions imposed by the pulse sequence chosen for double-quantum recoupling. We demonstrate the efficacy of SEASHORE in experimental 13C NMR measurements of frequency-selective polarization transfer in uniformly 15N, 13C-labeled L-valine powder and frequency-selective intermolecular polarization transfer in amyloid fibrils formed by a synthetic decapeptide containing uniformly 15N, 13C-labeled residues.
CAESURA: Measurement of slow molecular dynamics by solid-state nuclear magnetic resonance chemical shift anisotropy modulation amplification
The Journal of Chemical Physics, 14 August 2006J. Chem. Phys. 125, 064507
Limin Shao and Jeremy J. Titman
An alternative magic angle spinning (MAS) exchange NMR experiment based on chemical shift anisotropy (CSA) amplification is described. The CSA amplification experiment correlates a standard MAS spectrum in the 2 dimension with a sideband pattern in 1 in which the intensities are identical to those expected for a sample spinning at some fraction 1/N of the actual rate r. In common with 2D-PASS, the isotropic shift appears only in the 2 dimension, and long acquisition times can be avoided without loss of resolution of different chemical sites. The new CSA amplification exchange experiment provides information about the time scale and geometry of molecular motions via their effect on the sideband intensities in a one-dimensional pattern. The one-dimensional patterns from different chemical sites are separated across two frequency dimensions according to the isotropic shifts.
Limin Shao and Jeremy J. Titman
An alternative magic angle spinning (MAS) exchange NMR experiment based on chemical shift anisotropy (CSA) amplification is described. The CSA amplification experiment correlates a standard MAS spectrum in the 2 dimension with a sideband pattern in 1 in which the intensities are identical to those expected for a sample spinning at some fraction 1/N of the actual rate r. In common with 2D-PASS, the isotropic shift appears only in the 2 dimension, and long acquisition times can be avoided without loss of resolution of different chemical sites. The new CSA amplification exchange experiment provides information about the time scale and geometry of molecular motions via their effect on the sideband intensities in a one-dimensional pattern. The one-dimensional patterns from different chemical sites are separated across two frequency dimensions according to the isotropic shifts.
The nuclear electric quadrupole moment of antimony from the molecular method
The Journal of Chemical Physics, 14 August 2006J. Chem. Phys. 125, 064301
Roberto L. A. Haiduke and Albérico B. F. da Silva
Relativistic Dirac-Coulomb (DC) Hartree-Fock calculations are employed to obtain the analytic electric field gradient (EFG) on the antimony nucleus in the SbN, SbP, SbF, and SbCl molecules. The electronic correlation contribution to the EFGs is included with the DC-CCSD(T) and DC-CCSD-T approaches, also in the four-component framework, using a finite-difference method. The total EFG results, along with the experimental nuclear quadrupole coupling constants from microwave spectroscopy, allow to derive the nuclear quadrupole moments of 121Sb and 123Sb, respectively, as –543(11) and –692(14) mb.
Roberto L. A. Haiduke and Albérico B. F. da Silva
Relativistic Dirac-Coulomb (DC) Hartree-Fock calculations are employed to obtain the analytic electric field gradient (EFG) on the antimony nucleus in the SbN, SbP, SbF, and SbCl molecules. The electronic correlation contribution to the EFGs is included with the DC-CCSD(T) and DC-CCSD-T approaches, also in the four-component framework, using a finite-difference method. The total EFG results, along with the experimental nuclear quadrupole coupling constants from microwave spectroscopy, allow to derive the nuclear quadrupole moments of 121Sb and 123Sb, respectively, as –543(11) and –692(14) mb.
Ion and polymer dynamics in polymer electrolytes PPO-LiClO4. I. Insights from NMR line-shape analysis
The Journal of Chemical Physics, 7 August 2006J. Chem. Phys. 125, 054905
M. Vogel, and T. Torbrügge
We investigate ion and polymer dynamics in polymer electrolytes PPO-LiClO4 performing 2H and 7Li NMR line-shape analysis. Comparison of temperature dependent 7Li and 2H NMR spectra gives evidence for a coupling of ion and polymer dynamics. 2H NMR spectra for various salt concentrations reveal a strong slowdown of the polymer segmental motion when the salt content is increased. The 2H NMR line shape further indicates that the segmental motion is governed by dynamical heterogeneities. While the width of the distribution of correlation times G(log ) is moderate for low and high salt content, an extremely broad distribution exists for an intermediate salt concentration of 15:1 PPO-LiClO4. For the latter composition, a weighted superposition of two spectral components, reflecting the fast and the slow polymer segments of the distribution, describes the 2H NMR line shape over a broad temperature range. Analysis of the temperature dependent relative intensity of both spectral components indicates the existence of a continuous rather than a discontinuous distribution G(log ). Such continuous distribution is consistent with gradual fluctuations of the local salt concentration and, hence, of the local environments of the polymer segments, whereas it is at variance with the existence of large salt-depleted and salt-rich domains featuring fast and slow polymer dynamics, respectively. Finally, for all studied PPO-LiClO4 mixtures, the 2H NMR line shape strongly depends on the echo delay in the applied echo-pulse sequence, indicating that the structural relaxation of the polymer segments involves successive rotational jumps about small angles <20°.
M. Vogel, and T. Torbrügge
We investigate ion and polymer dynamics in polymer electrolytes PPO-LiClO4 performing 2H and 7Li NMR line-shape analysis. Comparison of temperature dependent 7Li and 2H NMR spectra gives evidence for a coupling of ion and polymer dynamics. 2H NMR spectra for various salt concentrations reveal a strong slowdown of the polymer segmental motion when the salt content is increased. The 2H NMR line shape further indicates that the segmental motion is governed by dynamical heterogeneities. While the width of the distribution of correlation times G(log ) is moderate for low and high salt content, an extremely broad distribution exists for an intermediate salt concentration of 15:1 PPO-LiClO4. For the latter composition, a weighted superposition of two spectral components, reflecting the fast and the slow polymer segments of the distribution, describes the 2H NMR line shape over a broad temperature range. Analysis of the temperature dependent relative intensity of both spectral components indicates the existence of a continuous rather than a discontinuous distribution G(log ). Such continuous distribution is consistent with gradual fluctuations of the local salt concentration and, hence, of the local environments of the polymer segments, whereas it is at variance with the existence of large salt-depleted and salt-rich domains featuring fast and slow polymer dynamics, respectively. Finally, for all studied PPO-LiClO4 mixtures, the 2H NMR line shape strongly depends on the echo delay in the applied echo-pulse sequence, indicating that the structural relaxation of the polymer segments involves successive rotational jumps about small angles <20°.
17O nuclear quadrupole coupling constants of water bound to a metal ion: A gadolinium(III) case study
The Journal of Chemical Physics, 7 August 2006J. Chem. Phys. 125, 054503
Oleg V. Yazyev and Lothar Helm
Rotational correlation times of metal ion aqua complexes can be determined from 17O NMR relaxation rates if the quadrupole coupling constant of the bound water oxygen-17 nucleus is known. The rotational correlation time is an important parameter for the efficiency of Gd3+ complexes as magnetic resonance imaging contrast agents. Using a combination of density functional theory with classical and Car-Parrinello molecular dynamics simulations we performed a computational study of the 17O quadrupole coupling constants in model aqua ions and the [Gd(DOTA)(H2O)]– complex used in clinical diagnostics. For the inner sphere water molecule in the [Gd(DOTA)(H2O)]– complex the determined quadrupole coupling parameter of 8.7 MHz is very similar to that of the liquid water (9.0 MHz). Very close values were also predicted for the the homoleptic aqua ions of Gd3+ and Ca2+. We conclude that the 17O quadrupole coupling parameters of water molecules coordinated to closed shell and lanthanide metal ions are similar to water molecules in the liquid state.
Oleg V. Yazyev and Lothar Helm
Rotational correlation times of metal ion aqua complexes can be determined from 17O NMR relaxation rates if the quadrupole coupling constant of the bound water oxygen-17 nucleus is known. The rotational correlation time is an important parameter for the efficiency of Gd3+ complexes as magnetic resonance imaging contrast agents. Using a combination of density functional theory with classical and Car-Parrinello molecular dynamics simulations we performed a computational study of the 17O quadrupole coupling constants in model aqua ions and the [Gd(DOTA)(H2O)]– complex used in clinical diagnostics. For the inner sphere water molecule in the [Gd(DOTA)(H2O)]– complex the determined quadrupole coupling parameter of 8.7 MHz is very similar to that of the liquid water (9.0 MHz). Very close values were also predicted for the the homoleptic aqua ions of Gd3+ and Ca2+. We conclude that the 17O quadrupole coupling parameters of water molecules coordinated to closed shell and lanthanide metal ions are similar to water molecules in the liquid state.
Wednesday, August 16, 2006
Sharon Ashbrook: 23Na MQMAS, Structure Determination via SSNMR and PXRD
Inorg. Chem., 45 (15), 6034 -6040, 2006. 10.1021/ic060483t S0020-1669(06)00483-6 Web Release Date: June 22, 2006 Copyright © 2006 American Chemical Society
Na2[(VO)2(HPO4)2C2O4]·2H2O: Crystal Structure Determination from Combined Powder Diffraction and Solid-State NMR
J. F. Colin, T. Bataille, S. E. Ashbrook, N. Audebrand, L. Le Pollès, J. Y. Pivan, and E. Le Fur*
Sciences Chimiques de Rennes, UMR 6226, CNRS-Université de Rennes 1-ENSCR, 35042 Rennes Cedex, France, and Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K.
Received March 22, 2006
Abstract: The vanadyl oxalatophosphate Na2[(VO)2(HPO4)2C2O4]·2H2O has been synthesized by hydrothermal treatment. Its structure has been determined and refined by combining X-ray powder diffraction and solid-state NMR techniques. It crystallizes with monoclinic symmetry in space group P21, a = 6.3534(1) Å, b = 17.1614(3) Å, c = 6.5632(1) Å, = 106.597(1). The structure is related to that of (NH4)2[(VO)2(HPO4)2C2O4]·5H2O, which was previously reported. The vanadium phosphate framework consists of infinite [(VO)(HPO4)] chains of corner-sharing vanadium octahedra and hydrogenophosphate tetrahedra. The oxalate groups ensure the connection between the chains to form a 2D structure. The sodium ions and the water molecules are located between the anionic [(VO)2(HPO4)2C2O4]2- layers. The thermal decomposition has been studied in situ by temperature-dependent X-ray diffraction and thermogravimetry. It takes place in three stages, where the first two correspond to water removal and the last to the decomposition of the oxalate group and water elimination, leading to the final product NaVOPO4.
Na2[(VO)2(HPO4)2C2O4]·2H2O: Crystal Structure Determination from Combined Powder Diffraction and Solid-State NMR
J. F. Colin, T. Bataille, S. E. Ashbrook, N. Audebrand, L. Le Pollès, J. Y. Pivan, and E. Le Fur*
Sciences Chimiques de Rennes, UMR 6226, CNRS-Université de Rennes 1-ENSCR, 35042 Rennes Cedex, France, and Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K.
Received March 22, 2006
Abstract: The vanadyl oxalatophosphate Na2[(VO)2(HPO4)2C2O4]·2H2O has been synthesized by hydrothermal treatment. Its structure has been determined and refined by combining X-ray powder diffraction and solid-state NMR techniques. It crystallizes with monoclinic symmetry in space group P21, a = 6.3534(1) Å, b = 17.1614(3) Å, c = 6.5632(1) Å, = 106.597(1). The structure is related to that of (NH4)2[(VO)2(HPO4)2C2O4]·5H2O, which was previously reported. The vanadium phosphate framework consists of infinite [(VO)(HPO4)] chains of corner-sharing vanadium octahedra and hydrogenophosphate tetrahedra. The oxalate groups ensure the connection between the chains to form a 2D structure. The sodium ions and the water molecules are located between the anionic [(VO)2(HPO4)2C2O4]2- layers. The thermal decomposition has been studied in situ by temperature-dependent X-ray diffraction and thermogravimetry. It takes place in three stages, where the first two correspond to water removal and the last to the decomposition of the oxalate group and water elimination, leading to the final product NaVOPO4.
Tuesday, August 15, 2006
113Cd NMR
Dalton Trans., 2006, 3534 - 3543, DOI: 10.1039/b601665k
Cadmium-113 NMR studies on homoleptic complexes containing thioether ligands: the crystal structures of [Cd([12]aneS4)2](ClO4)2, [Cd([18]aneS4N2)](PF6)2 and [Cd([9]aneS3)2](PF6)2
Monte L. Helm, Lensey L. Hill, John P. Lee, Donald G. Van Derveer and Gregory J. Grant
We report the measurement of 113Cd NMR chemical shift data for homoleptic thioether and related aza and mixed aza/thiacrown complexes. In a series of Cd(II) complexes containing trithioether to hexathioether ligands, we observe solution 113Cd NMR chemical shifts in the range of 225 to 731 ppm. Upfield chemical shifts in these NMR spectra are seen whenever: (a) the number of thioether sulfur donors in the complex is decreased, (b) a thioether sulfur donor is replaced by a secondary nitrogen donor, or (c) the size of the macrocycle ring increases without a change in the nature or number of the donor atoms. Changes in the identity of non-coordinating anions such as perchlorate or hexafluorophosphate have little effect upon the 113Cd NMR chemical shift in solution. We report the X-ray structure of the complex [Cd([12]aneS4)2](ClO4)2 ([12]aneS4 = 1,4,7,10-tetrathiacyclododecane) (1) which shows the first example of octakis(thioether) coordination of a metal ion, forming an unusual eight-coordinate square antiprismatic structure. We report the X-ray structure of the complex [Cd([9]aneS3)2](PF6)2 ([9]aneS3 = 1,4,7-trithiacyclononane) (3a) which shows hexakis(thioether) coordination to form a distorted octahedral structure. We have also prepared and characterized the Cd(II) complex of a mixed azathiacrown, [Cd([18]aneS4N2)](PF6)2 ([18]aneS4N2 = 1,4,10,13-tetrathia-7,16-diazacyclooctadecane) (6). Its X-ray structure shows a distorted octahedral S4N2 environment around the Cd(II) with the ligand coordinated in the rac fashion. We observe a solvent- and temperature-dependent 14N–1H coupling in the 1H NMR spectrum of the complex which is not present in analogous complexes with this ligand.
Cadmium-113 NMR studies on homoleptic complexes containing thioether ligands: the crystal structures of [Cd([12]aneS4)2](ClO4)2, [Cd([18]aneS4N2)](PF6)2 and [Cd([9]aneS3)2](PF6)2
Monte L. Helm, Lensey L. Hill, John P. Lee, Donald G. Van Derveer and Gregory J. Grant
We report the measurement of 113Cd NMR chemical shift data for homoleptic thioether and related aza and mixed aza/thiacrown complexes. In a series of Cd(II) complexes containing trithioether to hexathioether ligands, we observe solution 113Cd NMR chemical shifts in the range of 225 to 731 ppm. Upfield chemical shifts in these NMR spectra are seen whenever: (a) the number of thioether sulfur donors in the complex is decreased, (b) a thioether sulfur donor is replaced by a secondary nitrogen donor, or (c) the size of the macrocycle ring increases without a change in the nature or number of the donor atoms. Changes in the identity of non-coordinating anions such as perchlorate or hexafluorophosphate have little effect upon the 113Cd NMR chemical shift in solution. We report the X-ray structure of the complex [Cd([12]aneS4)2](ClO4)2 ([12]aneS4 = 1,4,7,10-tetrathiacyclododecane) (1) which shows the first example of octakis(thioether) coordination of a metal ion, forming an unusual eight-coordinate square antiprismatic structure. We report the X-ray structure of the complex [Cd([9]aneS3)2](PF6)2 ([9]aneS3 = 1,4,7-trithiacyclononane) (3a) which shows hexakis(thioether) coordination to form a distorted octahedral structure. We have also prepared and characterized the Cd(II) complex of a mixed azathiacrown, [Cd([18]aneS4N2)](PF6)2 ([18]aneS4N2 = 1,4,10,13-tetrathia-7,16-diazacyclooctadecane) (6). Its X-ray structure shows a distorted octahedral S4N2 environment around the Cd(II) with the ligand coordinated in the rac fashion. We observe a solvent- and temperature-dependent 14N–1H coupling in the 1H NMR spectrum of the complex which is not present in analogous complexes with this ligand.
A Whole Bunch of Metallocene Chemistry!! (For Those Who Care)
Dalton Trans., 2006, 3313 - 3320, DOI: 10.1039/b604640a
Complexes of a gallium heterocycle with transition metal dicyclopentadienyl and cyclopentadienylcarbonyl fragments, and with a dialkylmanganese compound
Simon Aldridge, Robert J. Baker, Natalie D. Coombs, Cameron Jones, Richard P. Rose, Andrea Rossin and David J. Willock
The reactivity of several transition metal half sandwich complexes towards an anionic gallium(I) heterocyclic complex, [K(tmeda)][Ga{[N(Ar)C(H)]2}](Ar = C6H3Pri2-2,6), has been investigated. This has led to the anionic half sandwich complexes, [K(tmeda)][(C5H4R)M(CO)n[Ga{[N(Ar)C(H)]2}]](M = V, R = H, n= 3; M = Mn, R = Me, n= 2; M = Co, R = H, n= 1), which crystallographic studies show to form dimers (M = Mn and Co) or a polymer (M = V) through bridging potassium cations. The metal–gallium bond lengths in all complexes are very short which, combined with some spectroscopic evidence, is suggestive of M–Ga -bonding. Density functional theory studies of models of all complexes indicate that the level of back-bonding in these complexes is, however, minimal and of a similar order to that seen in analogous complexes incorporating neutral N-heterocyclic carbene ligands. Reactions of the metallocenes, [M(C5H4Me)2](M = V or Cr), with the digallane(4), [Ga{[N(Ar)C(H)]2}]2, have afforded the neutral complexes, [M(C5H4Me)2[Ga{[N(Ar)C(H)]2}]], which are thought to be formed via an initial oxidative insertion of the transition metal centre into the Ga–Ga bond of the digallane. X-Ray crystallography shows the complexes to be monomeric. One (M = V) reacts with one equivalent of [K(tmeda)][Ga{[N(Ar)C(H)]2}] to give the crystallographically characterised, anionic bis(gallyl)-complex, [K(tmeda)][V(C5H4Me)2[Ga{[N(Ar)C(H)]2}]2]. For comparison, the reaction of [K(tmeda)][Ga{[N(Ar)C(H)]2}] with [Mn{CH(SiMe3)2}2] was carried out and gave the monomeric, anionic complex, [K(tmeda)][Mn{CH(SiMe3)2}2[Ga{[N(Ar)C(H)]2}]].
Complexes of a gallium heterocycle with transition metal dicyclopentadienyl and cyclopentadienylcarbonyl fragments, and with a dialkylmanganese compound
Simon Aldridge, Robert J. Baker, Natalie D. Coombs, Cameron Jones, Richard P. Rose, Andrea Rossin and David J. Willock
The reactivity of several transition metal half sandwich complexes towards an anionic gallium(I) heterocyclic complex, [K(tmeda)][Ga{[N(Ar)C(H)]2}](Ar = C6H3Pri2-2,6), has been investigated. This has led to the anionic half sandwich complexes, [K(tmeda)][(C5H4R)M(CO)n[Ga{[N(Ar)C(H)]2}]](M = V, R = H, n= 3; M = Mn, R = Me, n= 2; M = Co, R = H, n= 1), which crystallographic studies show to form dimers (M = Mn and Co) or a polymer (M = V) through bridging potassium cations. The metal–gallium bond lengths in all complexes are very short which, combined with some spectroscopic evidence, is suggestive of M–Ga -bonding. Density functional theory studies of models of all complexes indicate that the level of back-bonding in these complexes is, however, minimal and of a similar order to that seen in analogous complexes incorporating neutral N-heterocyclic carbene ligands. Reactions of the metallocenes, [M(C5H4Me)2](M = V or Cr), with the digallane(4), [Ga{[N(Ar)C(H)]2}]2, have afforded the neutral complexes, [M(C5H4Me)2[Ga{[N(Ar)C(H)]2}]], which are thought to be formed via an initial oxidative insertion of the transition metal centre into the Ga–Ga bond of the digallane. X-Ray crystallography shows the complexes to be monomeric. One (M = V) reacts with one equivalent of [K(tmeda)][Ga{[N(Ar)C(H)]2}] to give the crystallographically characterised, anionic bis(gallyl)-complex, [K(tmeda)][V(C5H4Me)2[Ga{[N(Ar)C(H)]2}]2]. For comparison, the reaction of [K(tmeda)][Ga{[N(Ar)C(H)]2}] with [Mn{CH(SiMe3)2}2] was carried out and gave the monomeric, anionic complex, [K(tmeda)][Mn{CH(SiMe3)2}2[Ga{[N(Ar)C(H)]2}]].
195Pt NMR and DFT computational methods as tools towards the understanding of speciation and hydration/solvation of [PtX6]2– (X = Cl–, Br–) anions in
Dalton Trans., 2006, 3277 - 3284, DOI: 10.1039/b605182k
195Pt NMR and DFT computational methods as tools towards the understanding of speciation and hydration/solvation of [PtX6]2– (X = Cl–, Br–) anions in solution
Klaus R. Koch, M. R. Burger, J. Kramer and A. N. Westra
195Pt NMR together with DFT calculations and MD simulations, offer a powerful toolkit with which to probe the hydration shells of the [PtCl6]2– anions, which may lead to a more profound understanding of the solute–solvent interactions of such complexes.
195Pt NMR and DFT computational methods as tools towards the understanding of speciation and hydration/solvation of [PtX6]2– (X = Cl–, Br–) anions in solution
Klaus R. Koch, M. R. Burger, J. Kramer and A. N. Westra
195Pt NMR together with DFT calculations and MD simulations, offer a powerful toolkit with which to probe the hydration shells of the [PtCl6]2– anions, which may lead to a more profound understanding of the solute–solvent interactions of such complexes.
Chem. Mater. 45Sc NMR of Solid Oxides and Stablized Zirconia, Stebbins
Web Release Date: July 7,
Scandium Coordination in Solid Oxides and Stabilized Zirconia: 45Sc NMR
Departments of Geological and Environmental Sciences and Materials Science and Engineering, Stanford University, Stanford, California 94305
Abstract:
45Sc NMR isotropic chemical shifts and quadrupole coupling constants of several scandium-containing solid oxides have been measured. Both parameters prove to be sensitive to local structure. In particular, in these materials the 45Sc isotropic chemical shift appears to be dominated by the first neighbor coordination environment, i.e., the coordination number. The difference in the isotropic shifts between six-coordinated and eight-coordinated scandium is more than 150 ppm, suggesting that this parameter may be especially useful in studying the scandium coordination in oxide materials, disordered solids in particular. Quadrupole coupling constants are sensitive to the nature of the second coordination cation, although many other structural details may play a role. The chemical shift correlation was applied to scandia-stabilized zirconia, (ZrO2)0.92(Sc2O3)0.08, and the mean coordination number obtained appears to be close to seven, which suggests the possibility of two scandium cations pairing with one vacancy.
Friday, August 11, 2006
Joel's Monthly Journal Update
Andy - Some CdSe papers
Fabrication of Stable Low-Density Silica Aerogels Containing Luminescent ZnS Capped CdSe Quantum Dots.
L. Sorensen, G.F. Strouse, and A.E. Stiegman.
Advan. Mat. (2006)18, 1965.
Summary:
Luminescent CdSe quantum dots of 2.5 and 6.0 nm dimension have been incorporated into a low-density silica aerogels matrix. The aerogels are formed from the supercritical CO2 extraction of an alcogel containing quantum dots surface passivated with 3-aminopropyltriethoxysilane. The resulting aerogels (see figure and cover) are low scattering and show intense, stable luminescence.
Growth of CdSe Quantum Rods and Multipods Seeded by Noble-Metal Nanoparticles.
K.T. Yong, Y. Sahoo, M.T. Swihart and P.N. Prasad
Advan. Mat. (2006)18, 1978.
Summary:
CdSe quantum rods are prepared at much milder conditions than previously reported, using noble-metal seed particles to initiate growth. The CdSe nanocrystals initially form as multipods that cleave to yield freestanding quantum rods (see figure) with high photoluminescence quantum yields. This study provides a new direction in developing facile syntheses of semiconductor NCs with nonspherical morphology, thereby making available new building blocks for nanotechnology.
Bryan - Au Nanoparticle Stuff
Turkevich Method for Gold Nanoparticle Synthesis Revisited
J. Kimling, M. Maier, B. Okenve, V. Kotaidis, H. Ballot, and A. Plech.
J.Phys.Chem.B(2006)110,15700.
Abstract:
The growth of gold nanoparticles by reduction by citrate and ascorbic acid has been examined in detail to explore the parameter space of reaction conditions. It is found that gold particles can be produced in a wide range of sizes, from 9 to 120 nm, with defined size distribution, following the earlier work of Turkevich and Frens. The reaction is initiated thermally or in comparison by UV irradiation, which results in similar final products. The kinetics of the extinction spectra show the multiple steps of primary and secondary clustering leading to polycrystallites.
Andre
Structural, Magnetic, and Spectroscopic Studies of YAgSn, TmAgSn, and LuAgSn
C.P. Sebastian, H. Eckert, C. Fehse, J.P. Wright, J.P. Attfield, D. Johrendt, S. Rayaprol, R.D. Hoffmann, R. Pottgen.
JSolidStateChem (2006) 179, 2376.
Abstract:
The rare earth–silver–stannides YAgSn, TmAgSn, and LuAgSn were synthesized from the elements by arc-melting and subsequent annealing. The three stannides were investigated by X-ray powder and single-crystal diffraction: NdPtSb type, P63mc, Z=2, a=468.3(1), Click to view the MathML sourcepm, wR2=0.0343, 353 F2 values, 12 variables for YAgSn, and ZrNiAl type, P6¯2 m, a=726.4(2), Click to view the MathML source, wR2=0.0399, 659 F2 values, 15 variables for TmAgSn, and a=723.8(2), Click to view the MathML source, wR2=0.0674, 364 F2 values, 15 variables for LuAgSn. Besides conventional laboratory X-ray data with monochromatized Mo radiation, the structures were also refined on the basis of synchrotron data with Click to view the MathML source, in order to clarify the silver–tin ordering more precisely. YAgSn has puckered, two-dimensional [AgSn] networks with Ag–Sn distances of 278 pm, while the [AgSn] networks of TmAgSn and LuAgSn are three-dimensional with Ag–Sn distances of 279 and 284 pm for LuAgSn. Susceptibility measurements indicate Pauli paramagnetism for YAgSn and LuAgSn. TmAgSn is a Curie–Weiss paramagnet with an experimental magnetic moment of 7.2 ?B/Tm. No magnetic ordering is evident down to 2 K. The local environments of the tin sites in these compounds were characterized by 119Sn Mössbauer spectroscopy and solid-state NMR (in YAgSn and LuAgSn), confirming the tin site multiplicities proposed from the structure solutions and the absence of Sn/Ag site disordering. Mössbauer quadrupolar splittings were found in good agreement with calculated electric field gradients predicted quantum chemically by the WIEN2k code. Furthermore, an excellent correlation was found between experimental 119Sn nuclear magnetic shielding anisotropies (determined via MAS-NMR) and calculated electric field gradients. Electronic structure calculations predict metallic properties with strong Ag–Sn bonds and also significant Ag–Ag bonding in LuAgSn.
Na->Li (and Li->Na) CP/MAS
Site Discrimination in Mixed-Alkali Glasses Studied by Cross-Polarization NMR
S.P. Puls and H. Eckert.
J.Phys.Chem.B(2006)110,14253.
Abstract:
Cation-cation interactions are thought to play a significant role in shaping the nonlinear compositional dependence of ionic conductivity, known as the mixed-alkali effect (MAE) in glassy solid electrolytes. For providing a structural rationale of this effect, the discrimination of various cation sites in mixed-alkali glasses is of interest. In the present study, cross-polarization (CP) experiments have been applied to glasses in the system [(Li2O)x(Na2O)1-x]0.3[B2O3]0.7 to discriminate between alkali ions by virtue of different heteronuclear 7Li-23Na dipole-dipole coupling strengths. Cross-polarization studies involving two types of quadrupolar nuclei (both 7Li and 23Na have a spin-quantum number I = 3/2) are complicated by spin state mixing under radio frequency irradiation and magic-angle spinning (MAS). Therefore careful validation and optimization protocols are reported for the model compound LiNaSO4 prior to conducting the measurements on the glassy samples. 23Na 7Li CP/MAS NMR spectra have been obtained on glasses containing the Na+ ions as the dilute species. They reveal that those lithium species interacting particularly strongly with sodium ions have the same average 7Li chemical shift as the entire lithium population; the symmetrical situation applies to the 23Na nuclei at the sodium rich end of the composition range. On the other hand, a clear site discrimination is afforded by temperature-dependent static 23Na 7Li CP experiments, indicating that the Li ions that are most strongly interacting with sodium ions are strongly immobilized. This finding provides the first direct experimental evidence for the proposed secondary mismatch concept invoked for explaining the strong MAE in the dilute foreign ion limit
Cory - 17O NMR and Repetitive DFS experiments
Sensitivity Enhancement and Heteronuclear Distance Measurements in Biological 17O Solid-State NMR
A. Binkmann and P.M. Kentgens
J.Phys.Chem.B(2006)110,16089.
Abstract:
In this contribution we present a comprehensive approach to study hydrogen bonding in biological and biomimetic systems through 17O and 17O-1H solid-state NMR combined with density functional theory calculations of 17O and 1H NMR parameters. We explore the signal enhancement of 17O in L-tyrosine·HCl using repetitive double-frequency swept radio frequency pulses in solid-state NMR. The technique is compatible with high magnetic fields and fast magic-angle spinning of the sample. A maximum enhancement by a factor of 4.3 is obtained in the signal-to-noise ratio of the selectively excited 17O central transition in a powdered sample of 17O-L-tyrosine·HCl at an external field of 14.1 T and a spinning frequency of 25 kHz. As little as 128 transients lead to meaningful 17O spectra of the same sample at an external field of 18.8 T and a spinning frequency of 50 kHz. Furthermore we employed supercycled symmetry-based pulse sequences on the protons to achieve heteronuclear longitudinal two-spin-order (IzSz) recoupling to determine 17O-1H distances. These sequences recouple the heteronuclear dipolar 17O-1H couplings, where dipolar truncation is absent, while decoupling the homonuclear proton dipolar interactions. They can be applied at fast magic-angle-spinning frequencies up and beyond 50 kHz and are very robust with respect to 17O quadrupolar couplings and both 17O and 1H chemical shift anisotropies, which makes them suitable for the use at high external magnetic fields. The method is demonstrated by determining the 17O-1H distance in L-tyrosine·HCl at a spinning frequency of 50 kHz and an external field of 18.8 T.
Fabrication of Stable Low-Density Silica Aerogels Containing Luminescent ZnS Capped CdSe Quantum Dots.
L. Sorensen, G.F. Strouse, and A.E. Stiegman.
Advan. Mat. (2006)18, 1965.
Summary:
Luminescent CdSe quantum dots of 2.5 and 6.0 nm dimension have been incorporated into a low-density silica aerogels matrix. The aerogels are formed from the supercritical CO2 extraction of an alcogel containing quantum dots surface passivated with 3-aminopropyltriethoxysilane. The resulting aerogels (see figure and cover) are low scattering and show intense, stable luminescence.
Growth of CdSe Quantum Rods and Multipods Seeded by Noble-Metal Nanoparticles.
K.T. Yong, Y. Sahoo, M.T. Swihart and P.N. Prasad
Advan. Mat. (2006)18, 1978.
Summary:
CdSe quantum rods are prepared at much milder conditions than previously reported, using noble-metal seed particles to initiate growth. The CdSe nanocrystals initially form as multipods that cleave to yield freestanding quantum rods (see figure) with high photoluminescence quantum yields. This study provides a new direction in developing facile syntheses of semiconductor NCs with nonspherical morphology, thereby making available new building blocks for nanotechnology.
Bryan - Au Nanoparticle Stuff
Turkevich Method for Gold Nanoparticle Synthesis Revisited
J. Kimling, M. Maier, B. Okenve, V. Kotaidis, H. Ballot, and A. Plech.
J.Phys.Chem.B(2006)110,15700.
Abstract:
The growth of gold nanoparticles by reduction by citrate and ascorbic acid has been examined in detail to explore the parameter space of reaction conditions. It is found that gold particles can be produced in a wide range of sizes, from 9 to 120 nm, with defined size distribution, following the earlier work of Turkevich and Frens. The reaction is initiated thermally or in comparison by UV irradiation, which results in similar final products. The kinetics of the extinction spectra show the multiple steps of primary and secondary clustering leading to polycrystallites.
Andre
Structural, Magnetic, and Spectroscopic Studies of YAgSn, TmAgSn, and LuAgSn
C.P. Sebastian, H. Eckert, C. Fehse, J.P. Wright, J.P. Attfield, D. Johrendt, S. Rayaprol, R.D. Hoffmann, R. Pottgen.
JSolidStateChem (2006) 179, 2376.
Abstract:
The rare earth–silver–stannides YAgSn, TmAgSn, and LuAgSn were synthesized from the elements by arc-melting and subsequent annealing. The three stannides were investigated by X-ray powder and single-crystal diffraction: NdPtSb type, P63mc, Z=2, a=468.3(1), Click to view the MathML sourcepm, wR2=0.0343, 353 F2 values, 12 variables for YAgSn, and ZrNiAl type, P6¯2 m, a=726.4(2), Click to view the MathML source, wR2=0.0399, 659 F2 values, 15 variables for TmAgSn, and a=723.8(2), Click to view the MathML source, wR2=0.0674, 364 F2 values, 15 variables for LuAgSn. Besides conventional laboratory X-ray data with monochromatized Mo radiation, the structures were also refined on the basis of synchrotron data with Click to view the MathML source, in order to clarify the silver–tin ordering more precisely. YAgSn has puckered, two-dimensional [AgSn] networks with Ag–Sn distances of 278 pm, while the [AgSn] networks of TmAgSn and LuAgSn are three-dimensional with Ag–Sn distances of 279 and 284 pm for LuAgSn. Susceptibility measurements indicate Pauli paramagnetism for YAgSn and LuAgSn. TmAgSn is a Curie–Weiss paramagnet with an experimental magnetic moment of 7.2 ?B/Tm. No magnetic ordering is evident down to 2 K. The local environments of the tin sites in these compounds were characterized by 119Sn Mössbauer spectroscopy and solid-state NMR (in YAgSn and LuAgSn), confirming the tin site multiplicities proposed from the structure solutions and the absence of Sn/Ag site disordering. Mössbauer quadrupolar splittings were found in good agreement with calculated electric field gradients predicted quantum chemically by the WIEN2k code. Furthermore, an excellent correlation was found between experimental 119Sn nuclear magnetic shielding anisotropies (determined via MAS-NMR) and calculated electric field gradients. Electronic structure calculations predict metallic properties with strong Ag–Sn bonds and also significant Ag–Ag bonding in LuAgSn.
Na->Li (and Li->Na) CP/MAS
Site Discrimination in Mixed-Alkali Glasses Studied by Cross-Polarization NMR
S.P. Puls and H. Eckert.
J.Phys.Chem.B(2006)110,14253.
Abstract:
Cation-cation interactions are thought to play a significant role in shaping the nonlinear compositional dependence of ionic conductivity, known as the mixed-alkali effect (MAE) in glassy solid electrolytes. For providing a structural rationale of this effect, the discrimination of various cation sites in mixed-alkali glasses is of interest. In the present study, cross-polarization (CP) experiments have been applied to glasses in the system [(Li2O)x(Na2O)1-x]0.3[B2O3]0.7 to discriminate between alkali ions by virtue of different heteronuclear 7Li-23Na dipole-dipole coupling strengths. Cross-polarization studies involving two types of quadrupolar nuclei (both 7Li and 23Na have a spin-quantum number I = 3/2) are complicated by spin state mixing under radio frequency irradiation and magic-angle spinning (MAS). Therefore careful validation and optimization protocols are reported for the model compound LiNaSO4 prior to conducting the measurements on the glassy samples. 23Na 7Li CP/MAS NMR spectra have been obtained on glasses containing the Na+ ions as the dilute species. They reveal that those lithium species interacting particularly strongly with sodium ions have the same average 7Li chemical shift as the entire lithium population; the symmetrical situation applies to the 23Na nuclei at the sodium rich end of the composition range. On the other hand, a clear site discrimination is afforded by temperature-dependent static 23Na 7Li CP experiments, indicating that the Li ions that are most strongly interacting with sodium ions are strongly immobilized. This finding provides the first direct experimental evidence for the proposed secondary mismatch concept invoked for explaining the strong MAE in the dilute foreign ion limit
Cory - 17O NMR and Repetitive DFS experiments
Sensitivity Enhancement and Heteronuclear Distance Measurements in Biological 17O Solid-State NMR
A. Binkmann and P.M. Kentgens
J.Phys.Chem.B(2006)110,16089.
Abstract:
In this contribution we present a comprehensive approach to study hydrogen bonding in biological and biomimetic systems through 17O and 17O-1H solid-state NMR combined with density functional theory calculations of 17O and 1H NMR parameters. We explore the signal enhancement of 17O in L-tyrosine·HCl using repetitive double-frequency swept radio frequency pulses in solid-state NMR. The technique is compatible with high magnetic fields and fast magic-angle spinning of the sample. A maximum enhancement by a factor of 4.3 is obtained in the signal-to-noise ratio of the selectively excited 17O central transition in a powdered sample of 17O-L-tyrosine·HCl at an external field of 14.1 T and a spinning frequency of 25 kHz. As little as 128 transients lead to meaningful 17O spectra of the same sample at an external field of 18.8 T and a spinning frequency of 50 kHz. Furthermore we employed supercycled symmetry-based pulse sequences on the protons to achieve heteronuclear longitudinal two-spin-order (IzSz) recoupling to determine 17O-1H distances. These sequences recouple the heteronuclear dipolar 17O-1H couplings, where dipolar truncation is absent, while decoupling the homonuclear proton dipolar interactions. They can be applied at fast magic-angle-spinning frequencies up and beyond 50 kHz and are very robust with respect to 17O quadrupolar couplings and both 17O and 1H chemical shift anisotropies, which makes them suitable for the use at high external magnetic fields. The method is demonstrated by determining the 17O-1H distance in L-tyrosine·HCl at a spinning frequency of 50 kHz and an external field of 18.8 T.
Tuesday, August 08, 2006
MRC: 29Si and 27Al NMR of paramagnetic materials
Magnetic Resonance in Chemistry
Vol: 44, Issue: 9, September 2006
pp. 861 - 867
Title: Solid-state NMR spectra of paramagnetic silica-based materials: observation of 29Si and 27Al nuclei in the first coordination spheres of manganese ions
Authors: Bakhmutov, Vladimir I.a; Shpeizer, Boris G.a; Clearfield, Abrahama
Affiliations: a. Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842‐3012, USA
Keywords: 29Si; 27Al NMR; paramagnetic solids; relaxation
Abstract (English):
Some silica-based solids, prepared by the sol/gel method in the presence of high Mn2+ concentrations, have been characterized by the 29Si, 27Al MAS NMR spectra and 29Si T1 measurements. The single-pulse 29Si and 27Al MAS NMR spectra have shown broad spinning sideband patterns that are interpreted in terms of anisotropic bulky magnetic susceptibility (BMS) and dipole-field effects. In the absence of paramagnetic isotropic shifts, the 29Si and 27Al nuclei observed in the single-pulse NMR spectra have been assigned to nuclei remote from paramagnetic centers. It has been demonstrated that the 29Si and 27Al nuclei, which are in the vicinity of the manganese ions, can be detected by the Hahn-echo MAS NMR experiments at different carrier frequencies. Copyright © 2006 John Wiley & Sons, Ltd.
Vol: 44, Issue: 9, September 2006
pp. 861 - 867
Title: Solid-state NMR spectra of paramagnetic silica-based materials: observation of 29Si and 27Al nuclei in the first coordination spheres of manganese ions
Authors: Bakhmutov, Vladimir I.a; Shpeizer, Boris G.a; Clearfield, Abrahama
Affiliations: a. Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842‐3012, USA
Keywords: 29Si; 27Al NMR; paramagnetic solids; relaxation
Abstract (English):
Some silica-based solids, prepared by the sol/gel method in the presence of high Mn2+ concentrations, have been characterized by the 29Si, 27Al MAS NMR spectra and 29Si T1 measurements. The single-pulse 29Si and 27Al MAS NMR spectra have shown broad spinning sideband patterns that are interpreted in terms of anisotropic bulky magnetic susceptibility (BMS) and dipole-field effects. In the absence of paramagnetic isotropic shifts, the 29Si and 27Al nuclei observed in the single-pulse NMR spectra have been assigned to nuclei remote from paramagnetic centers. It has been demonstrated that the 29Si and 27Al nuclei, which are in the vicinity of the manganese ions, can be detected by the Hahn-echo MAS NMR experiments at different carrier frequencies. Copyright © 2006 John Wiley & Sons, Ltd.
MRC: 71Ga NMR; Grandinetti
Magnetic Resonance in Chemistry
Vol: 44, Issue: 9, September 2006
pp. 823 - 831
Title: Solid-state NMR characterization of 69Ga and 71Ga in crystalline solids
Authors: Ash, Jason T.a; Grandinetti, Philip J.a
Affiliations: a. Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210‐1173, USA
Keywords: gallium NMR; quadrupolar nuclei
Abstract (English):
Gallium model systems containing four- and six-coordinate gallium sites have been investigated using solid-state NMR. Measurement of the isotropic chemical shift and electric field gradient (EFG) have been performed at 9.4 T on a-Ga2O3, b-Ga2O3, LiGaO2, NaGaO2, KGaO2, Ga2(SO4)3, and LaGaO3 using a variety of techniques on both NMR active nuclei (69Ga and 71Ga) including static, high speed magic-angle spinning (MAS), satellite transition (ST) spectroscopy, and rotor-assisted population transfer (RAPT). The chemical shift is found to correlate well with the coordination number, with four-coordinate gallium having values of approximately 50 ppm and six-coordinate gallium having values near 225 ppm (referenced to 1 M gallium nitrate solution). The magnitude of the EFG is found to be correlated to the distortion of the gallium polyhedra, with the strained systems having EFGs of 3 × 1021 Vm-2 or more, while the less strained systems have values of 1.5 × 1021 Vm-2 or less. A plot of chemical shift versus EFG suggests that solid-state NMR of gallium oxyanions can be more discriminating than liquid state NMR chemical shifts alone. Copyright © 2006 John Wiley & Sons, Ltd.
Vol: 44, Issue: 9, September 2006
pp. 823 - 831
Title: Solid-state NMR characterization of 69Ga and 71Ga in crystalline solids
Authors: Ash, Jason T.a; Grandinetti, Philip J.a
Affiliations: a. Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, Ohio 43210‐1173, USA
Keywords: gallium NMR; quadrupolar nuclei
Abstract (English):
Gallium model systems containing four- and six-coordinate gallium sites have been investigated using solid-state NMR. Measurement of the isotropic chemical shift and electric field gradient (EFG) have been performed at 9.4 T on a-Ga2O3, b-Ga2O3, LiGaO2, NaGaO2, KGaO2, Ga2(SO4)3, and LaGaO3 using a variety of techniques on both NMR active nuclei (69Ga and 71Ga) including static, high speed magic-angle spinning (MAS), satellite transition (ST) spectroscopy, and rotor-assisted population transfer (RAPT). The chemical shift is found to correlate well with the coordination number, with four-coordinate gallium having values of approximately 50 ppm and six-coordinate gallium having values near 225 ppm (referenced to 1 M gallium nitrate solution). The magnitude of the EFG is found to be correlated to the distortion of the gallium polyhedra, with the strained systems having EFGs of 3 × 1021 Vm-2 or more, while the less strained systems have values of 1.5 × 1021 Vm-2 or less. A plot of chemical shift versus EFG suggests that solid-state NMR of gallium oxyanions can be more discriminating than liquid state NMR chemical shifts alone. Copyright © 2006 John Wiley & Sons, Ltd.
Chem. Soc. Rev. Solid-State 17O NMR, Ashbrook and Smith
Chem. Soc. Rev., 2006, 35, 718 - 735, DOI: 10.1039/b514051j
Solid state 17O NMR—an introduction to the background principles and applications to inorganic materials
Sharon E. Ashbrook and Mark E. Smith
Oxygen is a key chemical element and solid state NMR can provide unique insight into the its local environment. In the last decade there have been significant advances (sensitivity, resolution) in the NMR methodology for non-integer spin quadrupole nuclei such as oxygen and the background to these techniques is presented in this tutorial review. The information that the NMR parameters can provide about the local environment is explained through a series of illustrations from different areas of solid state chemistry and structural science of inorganic materials.
Solid state 17O NMR—an introduction to the background principles and applications to inorganic materials
Sharon E. Ashbrook and Mark E. Smith
Oxygen is a key chemical element and solid state NMR can provide unique insight into the its local environment. In the last decade there have been significant advances (sensitivity, resolution) in the NMR methodology for non-integer spin quadrupole nuclei such as oxygen and the background to these techniques is presented in this tutorial review. The information that the NMR parameters can provide about the local environment is explained through a series of illustrations from different areas of solid state chemistry and structural science of inorganic materials.
Concepts: Structural Information from Quadrupolar Nuclei in Solid State NMR . Sharon E. Ashbrook, Melinda J. Duer.
Concepts in Magnetic Resonance Part A
Volume 28A, Issue 3 , Pages 183 - 248
Special Issue: Structural Information from Quadrupolar Nuclei in Solid State NMR . Issue Edited by Sharon E. Ashbrook, Melinda J. Duer.
Published Online: 4 May 2006
Structural information from quadrupolar nuclei in solid state NMR
Sharon E. Ashbrook 1, Melinda J. Duer 2 *
1 School of Chemistry and EaStChem, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, United Kingdom
2 Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
Keywords
solid-state NMR • quadrupole coupling • quadrupolar nuclei • structure determination • magic-angle spinning • double rotation • dynamic-angle spinning • correlation spectroscopy • multiple-quantum magic-angle spinning • satellite-transition magic-angle spinning • multiple quantum • rotational resonance • rotational-echo double resonance • J-coupling • scalar coupling • computation/calculation of NMR parameters
Abstract
Solid-state NMR has become the method of choice for determining details of molecular-level structure in heterogeneous systems. Though spin-1/2 nuclei still form the core of most such studies, quadrupolar nuclei are increasingly being used. This review assesses what is currently possible, from achieving high-resolution spectra for quadrupolar nuclei (a prerequisite for most structure determination work), to forming correlation spectra which give qualitative details of spatial proximity of nuclei and the determination of internuclear distances, between quadrupolar spins and quadrupolar and spin-1/2 nuclei. Examples are given of each method discussed, and the advantages and disadvantages of the various experiments for different possible applications are assessed. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 183-248, 2006.
Volume 28A, Issue 3 , Pages 183 - 248
Special Issue: Structural Information from Quadrupolar Nuclei in Solid State NMR . Issue Edited by Sharon E. Ashbrook, Melinda J. Duer.
Published Online: 4 May 2006
Structural information from quadrupolar nuclei in solid state NMR
Sharon E. Ashbrook 1, Melinda J. Duer 2 *
1 School of Chemistry and EaStChem, University of St. Andrews, North Haugh, St. Andrews, KY16 9ST, United Kingdom
2 Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
Keywords
solid-state NMR • quadrupole coupling • quadrupolar nuclei • structure determination • magic-angle spinning • double rotation • dynamic-angle spinning • correlation spectroscopy • multiple-quantum magic-angle spinning • satellite-transition magic-angle spinning • multiple quantum • rotational resonance • rotational-echo double resonance • J-coupling • scalar coupling • computation/calculation of NMR parameters
Abstract
Solid-state NMR has become the method of choice for determining details of molecular-level structure in heterogeneous systems. Though spin-1/2 nuclei still form the core of most such studies, quadrupolar nuclei are increasingly being used. This review assesses what is currently possible, from achieving high-resolution spectra for quadrupolar nuclei (a prerequisite for most structure determination work), to forming correlation spectra which give qualitative details of spatial proximity of nuclei and the determination of internuclear distances, between quadrupolar spins and quadrupolar and spin-1/2 nuclei. Examples are given of each method discussed, and the advantages and disadvantages of the various experiments for different possible applications are assessed. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 183-248, 2006.
JMR: 2D, 1 pulse NMR (TOP NMR) of quadrupoles; Massiot and Grandinetti
Journal of Magnetic Resonance
Vol: 181, Issue: 2, August, 2006
pp. 310-315
Title: Two-dimensional one pulse MAS of half-integer quadrupolar nuclei
Authors: Massiot, Dominiquea; Hiet, Juliana; Pellerin, Nadiaa; Fayon, Francka; Deschamps, Michaela; Steuernagel, Stefanb; Grandinetti, Philip J.c
Affiliations: a. CRMHT-CNRS, UPR4212, 45071 Orléans cedex 2, France
b. Bruker-Biospin GMBH, 76287 Rheinstetten, Germany
c. Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, OH 43210-1173, USA
Keywords: Solid-state NMR; Half-integer quadrupolar nuclei; Spinning sidebands
Abstract (English):
We show that the two-dimensional one pulse (TOP) representation of magic-angle spinning nuclear magnetic resonance data of half-integer quadrupolar nuclei has significant advantages over the conventional one-dimensional spectrum. The TOP spectrum, which correlates NMR frequency to spinning sideband order, provides a rapid determination of the number of sites as well as the size of the their quadrupolar coupling. Additionally, synchronous acquisition spectra of the central and satellite transition resonances can be separated by different projections of the TOP spectrum, with higher resolution spectra often found in the satellite transitions projection. A previously perceived problem of centerband aliasing in TOP can be eliminated with an algorithm that uses larger subspectral widths and the sideband order dimension to distinguish centerbands from sidebands.
Vol: 181, Issue: 2, August, 2006
pp. 310-315
Title: Two-dimensional one pulse MAS of half-integer quadrupolar nuclei
Authors: Massiot, Dominiquea; Hiet, Juliana; Pellerin, Nadiaa; Fayon, Francka; Deschamps, Michaela; Steuernagel, Stefanb; Grandinetti, Philip J.c
Affiliations: a. CRMHT-CNRS, UPR4212, 45071 Orléans cedex 2, France
b. Bruker-Biospin GMBH, 76287 Rheinstetten, Germany
c. Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, OH 43210-1173, USA
Keywords: Solid-state NMR; Half-integer quadrupolar nuclei; Spinning sidebands
Abstract (English):
We show that the two-dimensional one pulse (TOP) representation of magic-angle spinning nuclear magnetic resonance data of half-integer quadrupolar nuclei has significant advantages over the conventional one-dimensional spectrum. The TOP spectrum, which correlates NMR frequency to spinning sideband order, provides a rapid determination of the number of sites as well as the size of the their quadrupolar coupling. Additionally, synchronous acquisition spectra of the central and satellite transition resonances can be separated by different projections of the TOP spectrum, with higher resolution spectra often found in the satellite transitions projection. A previously perceived problem of centerband aliasing in TOP can be eliminated with an algorithm that uses larger subspectral widths and the sideband order dimension to distinguish centerbands from sidebands.
JMR: 2D, 1 pulse NMR (TOP NMR) of quadrupoles; Massiot and Grandinetti
Journal of Magnetic Resonance
Vol: 181, Issue: 2, August, 2006
pp. 310-315
Title: Two-dimensional one pulse MAS of half-integer quadrupolar nuclei
Authors: Massiot, Dominiquea; Hiet, Juliana; Pellerin, Nadiaa; Fayon, Francka; Deschamps, Michaela; Steuernagel, Stefanb; Grandinetti, Philip J.c
Affiliations: a. CRMHT-CNRS, UPR4212, 45071 Orléans cedex 2, France
b. Bruker-Biospin GMBH, 76287 Rheinstetten, Germany
c. Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, OH 43210-1173, USA
Keywords: Solid-state NMR; Half-integer quadrupolar nuclei; Spinning sidebands
Abstract (English):
We show that the two-dimensional one pulse (TOP) representation of magic-angle spinning nuclear magnetic resonance data of half-integer quadrupolar nuclei has significant advantages over the conventional one-dimensional spectrum. The TOP spectrum, which correlates NMR frequency to spinning sideband order, provides a rapid determination of the number of sites as well as the size of the their quadrupolar coupling. Additionally, synchronous acquisition spectra of the central and satellite transition resonances can be separated by different projections of the TOP spectrum, with higher resolution spectra often found in the satellite transitions projection. A previously perceived problem of centerband aliasing in TOP can be eliminated with an algorithm that uses larger subspectral widths and the sideband order dimension to distinguish centerbands from sidebands.
Vol: 181, Issue: 2, August, 2006
pp. 310-315
Title: Two-dimensional one pulse MAS of half-integer quadrupolar nuclei
Authors: Massiot, Dominiquea; Hiet, Juliana; Pellerin, Nadiaa; Fayon, Francka; Deschamps, Michaela; Steuernagel, Stefanb; Grandinetti, Philip J.c
Affiliations: a. CRMHT-CNRS, UPR4212, 45071 Orléans cedex 2, France
b. Bruker-Biospin GMBH, 76287 Rheinstetten, Germany
c. Department of Chemistry, The Ohio State University, 120 W. 18th Avenue, Columbus, OH 43210-1173, USA
Keywords: Solid-state NMR; Half-integer quadrupolar nuclei; Spinning sidebands
Abstract (English):
We show that the two-dimensional one pulse (TOP) representation of magic-angle spinning nuclear magnetic resonance data of half-integer quadrupolar nuclei has significant advantages over the conventional one-dimensional spectrum. The TOP spectrum, which correlates NMR frequency to spinning sideband order, provides a rapid determination of the number of sites as well as the size of the their quadrupolar coupling. Additionally, synchronous acquisition spectra of the central and satellite transition resonances can be separated by different projections of the TOP spectrum, with higher resolution spectra often found in the satellite transitions projection. A previously perceived problem of centerband aliasing in TOP can be eliminated with an algorithm that uses larger subspectral widths and the sideband order dimension to distinguish centerbands from sidebands.
JMR; 13C MAS NMR of paramagnetics; Ishii
Journal of Magnetic Resonance
Vol: 181, Issue: 2, August, 2006
pp. 233-243
Title: Sensitivity enhancement, assignment, and distance measurement in 13C solid-state NMR spectroscopy for paramagnetic systems under fast magic angle spinning
Authors: Wickramasinghe, Nalinda P.a; Ishii, Yoshitakaa
Affiliations: a. Department of Chemistry, University of Illinois at Chicago, Chicago IL 60607, USA
Keywords: 13C solid-state NMR; Paramagnetic systems; Fast MAS; Sensitivity; Assignments; Distances
Abstract (English):
Despite success of previous studies, high-resolution solid-state NMR (SSNMR) of paramagnetic systems has been still largely unexplored because of limited sensitivity/resolution and difficulty in assignment due to large paramagnetic shifts. Recently, we demonstrated that an approach using very-fast magic angle spinning (VFMAS; spinning speed 20kHz) enhances resolution/sensitivity in 13C SSNMR for paramagnetic complexes [Y. Ishii, S. Chimon, N.P. Wickramasinghe, A new approach in 1D and 2D 13C high resolution solid-state NMR spectroscopy of paramagnetic organometallic complexes by very fast magic-angle spinning, J. Am. Chem. Soc. 125 (2003) 3438–3439]. In this study, we present a new strategy for sensitivity enhancement, signal assignment, and distance measurement in 13C SSNMR under VFMAS for unlabeled paramagnetic complexes using recoupling-based polarization transfer. As a robust alternative of cross-polarization (CP), rapid application of recoupling-based polarization transfer under VFMAS is proposed. In the present approach, a dipolar-based analog of INEPT (dipolar INEPT) methods is used for polarization transfer and a 13C signal is observed under VFMAS without 1H decoupling. The resulting low duty factor permits rapid signal accumulation without probe arcing at recycle times (3ms/scan) matched to short 1H T1 values of small paramagnetic systems (1ms). Experiments on Cu(dl-Ala)2 showed that the fast repetition approach under VFMAS provided sensitivity enhancement by a factor of 8–66 for a given sample, compared with the 13C MAS spectrum under moderate MAS at 5kHz. The applicability of this approach was also demonstrated for a more challenging system, Mn(acac)3, for which 13C and 1H paramagnetic shift dispersions reach 1500 and 700ppm, respectively. It was shown that effective-evolution-time dependence of transferred signals in dipolar INEPT permitted one to distinguish 13CH, 13CH2, 13CH3, Formula Not Shown groups in 1D experiments for Cu(dl-Ala)2 and Cu(Gly)2. Applications of this technique to 2D 13C/1H correlation NMR under VFMAS yielded reliable assignments of 1H resonances as well as 13C resonances for Cu(dl-Ala)2 and Mn(acac)3. Quantitative analysis of cross-peak intensities in 2D 13C/1H correlation NMR spectra of Cu(dl-Ala)2 provided distance information between non-bonded 13C–1H pairs in the paramagnetic system.
Vol: 181, Issue: 2, August, 2006
pp. 233-243
Title: Sensitivity enhancement, assignment, and distance measurement in 13C solid-state NMR spectroscopy for paramagnetic systems under fast magic angle spinning
Authors: Wickramasinghe, Nalinda P.a; Ishii, Yoshitakaa
Affiliations: a. Department of Chemistry, University of Illinois at Chicago, Chicago IL 60607, USA
Keywords: 13C solid-state NMR; Paramagnetic systems; Fast MAS; Sensitivity; Assignments; Distances
Abstract (English):
Despite success of previous studies, high-resolution solid-state NMR (SSNMR) of paramagnetic systems has been still largely unexplored because of limited sensitivity/resolution and difficulty in assignment due to large paramagnetic shifts. Recently, we demonstrated that an approach using very-fast magic angle spinning (VFMAS; spinning speed 20kHz) enhances resolution/sensitivity in 13C SSNMR for paramagnetic complexes [Y. Ishii, S. Chimon, N.P. Wickramasinghe, A new approach in 1D and 2D 13C high resolution solid-state NMR spectroscopy of paramagnetic organometallic complexes by very fast magic-angle spinning, J. Am. Chem. Soc. 125 (2003) 3438–3439]. In this study, we present a new strategy for sensitivity enhancement, signal assignment, and distance measurement in 13C SSNMR under VFMAS for unlabeled paramagnetic complexes using recoupling-based polarization transfer. As a robust alternative of cross-polarization (CP), rapid application of recoupling-based polarization transfer under VFMAS is proposed. In the present approach, a dipolar-based analog of INEPT (dipolar INEPT) methods is used for polarization transfer and a 13C signal is observed under VFMAS without 1H decoupling. The resulting low duty factor permits rapid signal accumulation without probe arcing at recycle times (3ms/scan) matched to short 1H T1 values of small paramagnetic systems (1ms). Experiments on Cu(dl-Ala)2 showed that the fast repetition approach under VFMAS provided sensitivity enhancement by a factor of 8–66 for a given sample, compared with the 13C MAS spectrum under moderate MAS at 5kHz. The applicability of this approach was also demonstrated for a more challenging system, Mn(acac)3, for which 13C and 1H paramagnetic shift dispersions reach 1500 and 700ppm, respectively. It was shown that effective-evolution-time dependence of transferred signals in dipolar INEPT permitted one to distinguish 13CH, 13CH2, 13CH3, Formula Not Shown groups in 1D experiments for Cu(dl-Ala)2 and Cu(Gly)2. Applications of this technique to 2D 13C/1H correlation NMR under VFMAS yielded reliable assignments of 1H resonances as well as 13C resonances for Cu(dl-Ala)2 and Mn(acac)3. Quantitative analysis of cross-peak intensities in 2D 13C/1H correlation NMR spectra of Cu(dl-Ala)2 provided distance information between non-bonded 13C–1H pairs in the paramagnetic system.
JMR; SW-FAM for static NMR of quadrupolar nuclei; Madhu
Journal of Magnetic Resonance
Vol: 181, Issue: 1, July, 2006
pp. 68-78
Title: Fast amplitude-modulated pulse trains with frequency sweep (SW-FAM) in static NMR of half-integer spin quadrupolar nuclei
Authors: Bräuniger, Thomasa; Hempel, Güntera; Madhu, P.K.b
Affiliations: a. Department of Physics, University of Halle, Friedemann-Bach-Platz 6, 06108 Halle, Germany
b. Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
Keywords: Static 27Al NMR; Half-integer spin; Quadrupolar nuclei; SW-FAM
Abstract (English):
In solid-state NMR of quadrupolar nuclei with half-integer spin I, fast amplitude-modulated (FAM) pulse trains have been utilised to enhance the intensity of the central-transition signal, by transferring spin population from the satellite transitions. In this paper, the signal-enhancement performance of the recently introduced SW-FAM pulse train with swept modulation frequency [T. Bräuniger, K. Ramaswamy, P.K. Madhu, Enhancement of the central-transition signal in static and magic-angle-spinning NMR of quadrupolar nuclei by frequency-swept fast amplitude-modulated pulses, Chem. Phys. Lett. 383 (2004) 403â??410] is explored in more detail for static spectra. It is shown that by sweeping the modulation frequencies linearly over the pulse pairs (SW(1/Ï?)-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SW(Ï?)-FAM). For static spectra of 27Al (I=5/2), better signal-enhancement performance is found for the SW(1/Ï?)-FAM sequence, as demonstrated both by experiments and numerical simulations.
Vol: 181, Issue: 1, July, 2006
pp. 68-78
Title: Fast amplitude-modulated pulse trains with frequency sweep (SW-FAM) in static NMR of half-integer spin quadrupolar nuclei
Authors: Bräuniger, Thomasa; Hempel, Güntera; Madhu, P.K.b
Affiliations: a. Department of Physics, University of Halle, Friedemann-Bach-Platz 6, 06108 Halle, Germany
b. Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
Keywords: Static 27Al NMR; Half-integer spin; Quadrupolar nuclei; SW-FAM
Abstract (English):
In solid-state NMR of quadrupolar nuclei with half-integer spin I, fast amplitude-modulated (FAM) pulse trains have been utilised to enhance the intensity of the central-transition signal, by transferring spin population from the satellite transitions. In this paper, the signal-enhancement performance of the recently introduced SW-FAM pulse train with swept modulation frequency [T. Bräuniger, K. Ramaswamy, P.K. Madhu, Enhancement of the central-transition signal in static and magic-angle-spinning NMR of quadrupolar nuclei by frequency-swept fast amplitude-modulated pulses, Chem. Phys. Lett. 383 (2004) 403â??410] is explored in more detail for static spectra. It is shown that by sweeping the modulation frequencies linearly over the pulse pairs (SW(1/Ï?)-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SW(Ï?)-FAM). For static spectra of 27Al (I=5/2), better signal-enhancement performance is found for the SW(1/Ï?)-FAM sequence, as demonstrated both by experiments and numerical simulations.
JMR: CSA recoupling; Duer
Journal of Magnetic Resonance
Vol: 181, Issue: 1, July, 2006
pp. 1-8
Title: Recoupling of chemical-shift anisotropy powder patterns in MAS NMR
Authors: Orr, Robin M.a; Duer, Melinda J.a
Affiliations: a. Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
Keywords: Solid-state NMR; Magic-angle spinning; Chemical-shift anisotropy; Recoupling
Abstract (English):
A comparison of three different implementations of the chemical-shift recoupling experiment of Tycko et al. [R. Tycko, G. Dabbagh, P.A. Mirau, Determination of chemical-shift-anisotropy lineshapes in a two-dimensional magic-angle-spinning NMR experiment, J. Magn. Reson. 85 (1989) 265â??274] is presented. The methods seek to reduce the effects of artefacts resulting from pulse imperfections and residual C-H dipolar coupling in organic solids. An optimised and constant time implementation are shown to give well-defined and artefact free powder pattern lineshapes in the indirectly observed dimension for both sp2 and sp3 carbon sites. Experimental setup is no more demanding than for the original experiment, and can be implemented using standard commercial hardware.
Vol: 181, Issue: 1, July, 2006
pp. 1-8
Title: Recoupling of chemical-shift anisotropy powder patterns in MAS NMR
Authors: Orr, Robin M.a; Duer, Melinda J.a
Affiliations: a. Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
Keywords: Solid-state NMR; Magic-angle spinning; Chemical-shift anisotropy; Recoupling
Abstract (English):
A comparison of three different implementations of the chemical-shift recoupling experiment of Tycko et al. [R. Tycko, G. Dabbagh, P.A. Mirau, Determination of chemical-shift-anisotropy lineshapes in a two-dimensional magic-angle-spinning NMR experiment, J. Magn. Reson. 85 (1989) 265â??274] is presented. The methods seek to reduce the effects of artefacts resulting from pulse imperfections and residual C-H dipolar coupling in organic solids. An optimised and constant time implementation are shown to give well-defined and artefact free powder pattern lineshapes in the indirectly observed dimension for both sp2 and sp3 carbon sites. Experimental setup is no more demanding than for the original experiment, and can be implemented using standard commercial hardware.
MRC: 31P-71Ga MAS HMQC experiments; gallophosphates; Massiot
Magnetic Resonance in Chemistry
Vol: 44, Issue: 8, August 2006
pp. 770 - 775
Title: Toward a better description of gallo-phosphate materials in solid-state NMR: 1D and 2D correlation studies
Authors: Montouillout, Valériea; Morais, Cláudia M.a; Douy, Andréa; Fayon, Francka; Massiot, Dominiquea
Affiliations: a. CRMHT—CNRS UPR4212 1D, Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France
Keywords: NMR; 71Ga; 31P; HMQC experiment; gallo-phosphates
Abstract (English):
We show that weak 2J(71Ga—O—31P), typically 12 Hz in GaPO4, can be used to efficiently establish heteronuclear 31P—71Ga correlation using a MAS HMQC experiment in gallo-phosphate materials. The experiment demonstrated for cristobalite GaPO4 is then applied to Ga(PO3)3, where it allows the differentiation of the signature of three different Ga sites overlapping in the 1D spectrum. Copyright © 2006 John Wiley & Sons, Ltd.
Vol: 44, Issue: 8, August 2006
pp. 770 - 775
Title: Toward a better description of gallo-phosphate materials in solid-state NMR: 1D and 2D correlation studies
Authors: Montouillout, Valériea; Morais, Cláudia M.a; Douy, Andréa; Fayon, Francka; Massiot, Dominiquea
Affiliations: a. CRMHT—CNRS UPR4212 1D, Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France
Keywords: NMR; 71Ga; 31P; HMQC experiment; gallo-phosphates
Abstract (English):
We show that weak 2J(71Ga—O—31P), typically 12 Hz in GaPO4, can be used to efficiently establish heteronuclear 31P—71Ga correlation using a MAS HMQC experiment in gallo-phosphate materials. The experiment demonstrated for cristobalite GaPO4 is then applied to Ga(PO3)3, where it allows the differentiation of the signature of three different Ga sites overlapping in the 1D spectrum. Copyright © 2006 John Wiley & Sons, Ltd.
MRC: 33S NMR of ethanesulfonates, plus DFT and NBO methods
Magnetic Resonance in Chemistry
Vol: 44, Issue: 8, August 2006
pp. 753 - 760
Title: 33S NMR spectroscopy 3. substituent effects on 33S NMR parameters in 2-substituted ethanesulfonates
Authors: Musio, Robertaa; Sciacovelli, Oronzoa
Affiliations: a. Istituto C.N.R. di Chimica dei Composti Organo‐Metallici—Sezione di Bari and Dipartimento di Chimica, Università degli Studi di Bari, Via E. Orabona 4, 70126 Bari, Italy
Keywords: NMR; 33S NMR; 33S chemical shift; 33S nuclear shielding calculations; 33S nuclear quadrupole coupling constant; substituent effect; 2-substituted ethanesulfonates
Abstract (English):
33S NMR parameters (chemical shifts and linewidths) in 2-substituted sodium ethanesulfonates, XCH2CH2SO3Na (X = H, CH3, OH, SH, NH2, Cl, Br, NH3+) depend upon the electronic properties of substituents. To explain experimental results and obtain additional information on the origin of the observed substituent effect (SE), sulfur isotropic absolute shielding constants have been calculated at DFT level of theory (B3LYP/6-311 + + G(2d,p)) by gauge-including atomic orbitals (GIAO) method. Data have been interpreted with the aid of natural bond orbital (NBO) method and natural chemical shielding (NCS) analysis. It has been demonstrated that in the class of compounds considered the diamagnetic contribution to sulfur-shielding constant is constant and the observed upfield shift of 33S resonance induced by electron-withdrawing substituents (reverse chemical shift effect) can be related to variations of the paramagnetic contribution. Substituents with different electronic properties cause variations in the polarization of S—C and S—O bonds of the —C—SO3- moiety thus determining changes of the electron density at sulfur nucleus and consequently the expansion or contraction of 3p sulfur orbitals. Also oxygen lone-pairs and sulfur core 2p electrons can play an active role in determining the paramagnetic contribution to sulfur shielding. With regard to linewidth variations, they can be ascribed primarily to changes in the nuclear quadrupole coupling constant values. B3LYP/6-311 + + G(2d,p) method allows obtaining a good reproducibility of SE on the electric field gradient (EFG) at sulfur, although its values tend to be underestimated significantly. Moreover, 17O shielding constants have been calculated. Copyright © 2006 John Wiley & Sons, Ltd.
Vol: 44, Issue: 8, August 2006
pp. 753 - 760
Title: 33S NMR spectroscopy 3. substituent effects on 33S NMR parameters in 2-substituted ethanesulfonates
Authors: Musio, Robertaa; Sciacovelli, Oronzoa
Affiliations: a. Istituto C.N.R. di Chimica dei Composti Organo‐Metallici—Sezione di Bari and Dipartimento di Chimica, Università degli Studi di Bari, Via E. Orabona 4, 70126 Bari, Italy
Keywords: NMR; 33S NMR; 33S chemical shift; 33S nuclear shielding calculations; 33S nuclear quadrupole coupling constant; substituent effect; 2-substituted ethanesulfonates
Abstract (English):
33S NMR parameters (chemical shifts and linewidths) in 2-substituted sodium ethanesulfonates, XCH2CH2SO3Na (X = H, CH3, OH, SH, NH2, Cl, Br, NH3+) depend upon the electronic properties of substituents. To explain experimental results and obtain additional information on the origin of the observed substituent effect (SE), sulfur isotropic absolute shielding constants have been calculated at DFT level of theory (B3LYP/6-311 + + G(2d,p)) by gauge-including atomic orbitals (GIAO) method. Data have been interpreted with the aid of natural bond orbital (NBO) method and natural chemical shielding (NCS) analysis. It has been demonstrated that in the class of compounds considered the diamagnetic contribution to sulfur-shielding constant is constant and the observed upfield shift of 33S resonance induced by electron-withdrawing substituents (reverse chemical shift effect) can be related to variations of the paramagnetic contribution. Substituents with different electronic properties cause variations in the polarization of S—C and S—O bonds of the —C—SO3- moiety thus determining changes of the electron density at sulfur nucleus and consequently the expansion or contraction of 3p sulfur orbitals. Also oxygen lone-pairs and sulfur core 2p electrons can play an active role in determining the paramagnetic contribution to sulfur shielding. With regard to linewidth variations, they can be ascribed primarily to changes in the nuclear quadrupole coupling constant values. B3LYP/6-311 + + G(2d,p) method allows obtaining a good reproducibility of SE on the electric field gradient (EFG) at sulfur, although its values tend to be underestimated significantly. Moreover, 17O shielding constants have been calculated. Copyright © 2006 John Wiley & Sons, Ltd.
MRC; DFT of 53Cr chemical shielding; Buhl
Magnetic Resonance in Chemistry
Vol: 44, Issue: 7, July 2006
pp. 661 - 668
Title: Density-functional computation of 53Cr NMR chemical shifts
Author: Bühl, Michaela
Affiliations: a. Max‐Planck Institut für Kohlenforschung, Kaiser‐Wilhelm Platz 1, D‐45470 Mülheim an der Ruhr, Germany
Keywords: NMR; 53Cr; density-functional calculations; chemical-shift computations; electric field gradients
Abstract (English):
53Cr chemical shifts of CrO42-, Cr2O72-, CrO3X-, CrO2X2(X = F, Cl), and Cr(CO)5L (L = CO, PF3, CHNH2, CMeNMe2) are computed, using geometries optimized with the gradient-corrected BP86 density functional, at the gauge-including atomic orbitals (GIAO)-, BPW91-, and B3LYP levels. For this set of compounds, substituent effects on d(53Cr) are better described with the pure BPW91 functional than with B3LYP, in contrast to most other transition-metal chemical shifts studied so far. For selected cases, 53Cr NMR line widths can be rationalized in terms of electric field gradients (EFGs) computed with the BPW91 functional, but in general other factors such as molecular correlation times appear to be dominating. 53Cr chemical shifts and EFGs are predicted for CrO3, Cr(C6H6)2, Cr(C6H6)CO3, and, with reduced reliability, for Cr2(m2-O2CH)4. Copyright © 2006 John Wiley & Sons, Ltd.
Vol: 44, Issue: 7, July 2006
pp. 661 - 668
Title: Density-functional computation of 53Cr NMR chemical shifts
Author: Bühl, Michaela
Affiliations: a. Max‐Planck Institut für Kohlenforschung, Kaiser‐Wilhelm Platz 1, D‐45470 Mülheim an der Ruhr, Germany
Keywords: NMR; 53Cr; density-functional calculations; chemical-shift computations; electric field gradients
Abstract (English):
53Cr chemical shifts of CrO42-, Cr2O72-, CrO3X-, CrO2X2(X = F, Cl), and Cr(CO)5L (L = CO, PF3, CHNH2, CMeNMe2) are computed, using geometries optimized with the gradient-corrected BP86 density functional, at the gauge-including atomic orbitals (GIAO)-, BPW91-, and B3LYP levels. For this set of compounds, substituent effects on d(53Cr) are better described with the pure BPW91 functional than with B3LYP, in contrast to most other transition-metal chemical shifts studied so far. For selected cases, 53Cr NMR line widths can be rationalized in terms of electric field gradients (EFGs) computed with the BPW91 functional, but in general other factors such as molecular correlation times appear to be dominating. 53Cr chemical shifts and EFGs are predicted for CrO3, Cr(C6H6)2, Cr(C6H6)CO3, and, with reduced reliability, for Cr2(m2-O2CH)4. Copyright © 2006 John Wiley & Sons, Ltd.
MRC: 13C SSNMR of taxol
Magnetic Resonance in Chemistry
Vol: 44, Issue: 6, May 2006
pp. 581 - 585
Title: Solid-state NMR studies of the molecular structure of Taxol
Authors: Ho, Yua; Tzou, Der-Lii M.; Chu, Feng-Ia
Affiliations: a. Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529, Taiwan, Republic of China
Keywords: NMR; 13C; Taxol; molecular conformation
Abstract (English):
Solid-state 13C{1H} cross-polarization/magic angle spinning spectroscopy (CP/MAS) has been utilized to extract the molecular structure information of Taxol, which is an anti-tumor therapeutic medicine extracted from the yew bark. The 13C signals have chemical shift values quite consistent with those measured in solution phase, and the overall chemical shift range is over 200 ppm. Notably, most of the 13C resonances of the taxane ring have two clearly resolved spectral components except the resonance peaks of C-15, C-16 and C-17, which are located at the central part of the taxane ring. On the basis of our NMR data, we propose that these doublets originate from two slightly different molecular conformations of the taxane ring and still the central part of the ring remains structurally similar. Furthermore, it is demonstrated that the 13C chemical shift difference deduced from the doublet splittings can serve as a direct measure of the structural difference between the two conformations, which could possibly correlate with the anti-tumor activity of Taxol. Copyright © 2006 John Wiley & Sons, Ltd.
Vol: 44, Issue: 6, May 2006
pp. 581 - 585
Title: Solid-state NMR studies of the molecular structure of Taxol
Authors: Ho, Yua; Tzou, Der-Lii M.; Chu, Feng-Ia
Affiliations: a. Institute of Chemistry, Academia Sinica, Nankang, Taipei 11529, Taiwan, Republic of China
Keywords: NMR; 13C; Taxol; molecular conformation
Abstract (English):
Solid-state 13C{1H} cross-polarization/magic angle spinning spectroscopy (CP/MAS) has been utilized to extract the molecular structure information of Taxol, which is an anti-tumor therapeutic medicine extracted from the yew bark. The 13C signals have chemical shift values quite consistent with those measured in solution phase, and the overall chemical shift range is over 200 ppm. Notably, most of the 13C resonances of the taxane ring have two clearly resolved spectral components except the resonance peaks of C-15, C-16 and C-17, which are located at the central part of the taxane ring. On the basis of our NMR data, we propose that these doublets originate from two slightly different molecular conformations of the taxane ring and still the central part of the ring remains structurally similar. Furthermore, it is demonstrated that the 13C chemical shift difference deduced from the doublet splittings can serve as a direct measure of the structural difference between the two conformations, which could possibly correlate with the anti-tumor activity of Taxol. Copyright © 2006 John Wiley & Sons, Ltd.
MRC; ssnmr of nanocrystalline hydroxyapatite; Jäger
Magnetic Resonance in Chemistry
Vol: 44, Issue: 6, May 2006
pp. 573 - 580
Title: A solid-state NMR investigation of the structure of nanocrystalline hydroxyapatite
Authors: Jäger, Christiana; Welzel, Theab; Meyer-Zaika, Wolfgangb; Epple, Matthiasb
Affiliations: a. Federal Institute for Materials Research and Testing, Division I.3, Working Group NMR Spectroscopy, Richard Willstaetter Str. 11, D‐12489 Berlin, Germany
b. Institute of Inorganic Chemistry, University Duisburg‐Essen, Universitaetsstr. 5‐7, D‐45117 Essen, Germany
Keywords: NMR; 1H; 31P; biomineralization; hydroxyapatite; calcium phosphate; nanoparticles
Abstract (English):
Nanocrystalline hydroxyapatite (HAp) prepared by a precipitation route was investigated. The X-ray diffraction (XRD) powder patterns of the elongated nanocrystals with a typical diameter of about 10 nm and length of 30–50 nm (by transmission electron microscopy (TEM)) revealed the presence of HAp with significantly broadened XRD reflections. However, Ca deficiency was found, as the Ca/P ratio was 1.5 only (so-called calcium-deficient hydroxyapatite (CDHA)), and not 1.67. This Ca deficiency of nanocrystalline HAp is explained using NMR. It is shown unambiguously that (i) the nanocrystals consist of a crystalline core and a (disordered) surface region with a relative phosphate content of about 1:1, (ii) the crystalline core is HAp, and (iii) the surface region is dominated by hydrogen phosphate anions (with no hydroxyapatite-like structural motif) and structural water (hydrate). From the relative phosphate content and taking into account the crystal shape, the thickness of the surface layer along the main crystal axis could be estimated to be about 1 nm, and the average chemical composition of the surface layer has been determined. Finally, a Ca/P ratio of 1.52 was estimated from the NMR data that compares well with the value of 1.51 from chemical analysis. The important consequences are that the surface of nanocrystalline HAp has nothing in common with the bulk composition and that the chemistry of such materials (e.g. the binding of protein molecules to phosphate surfaces) must be reconsidered. Copyright © 2006 John Wiley & Sons, Ltd.
Vol: 44, Issue: 6, May 2006
pp. 573 - 580
Title: A solid-state NMR investigation of the structure of nanocrystalline hydroxyapatite
Authors: Jäger, Christiana; Welzel, Theab; Meyer-Zaika, Wolfgangb; Epple, Matthiasb
Affiliations: a. Federal Institute for Materials Research and Testing, Division I.3, Working Group NMR Spectroscopy, Richard Willstaetter Str. 11, D‐12489 Berlin, Germany
b. Institute of Inorganic Chemistry, University Duisburg‐Essen, Universitaetsstr. 5‐7, D‐45117 Essen, Germany
Keywords: NMR; 1H; 31P; biomineralization; hydroxyapatite; calcium phosphate; nanoparticles
Abstract (English):
Nanocrystalline hydroxyapatite (HAp) prepared by a precipitation route was investigated. The X-ray diffraction (XRD) powder patterns of the elongated nanocrystals with a typical diameter of about 10 nm and length of 30–50 nm (by transmission electron microscopy (TEM)) revealed the presence of HAp with significantly broadened XRD reflections. However, Ca deficiency was found, as the Ca/P ratio was 1.5 only (so-called calcium-deficient hydroxyapatite (CDHA)), and not 1.67. This Ca deficiency of nanocrystalline HAp is explained using NMR. It is shown unambiguously that (i) the nanocrystals consist of a crystalline core and a (disordered) surface region with a relative phosphate content of about 1:1, (ii) the crystalline core is HAp, and (iii) the surface region is dominated by hydrogen phosphate anions (with no hydroxyapatite-like structural motif) and structural water (hydrate). From the relative phosphate content and taking into account the crystal shape, the thickness of the surface layer along the main crystal axis could be estimated to be about 1 nm, and the average chemical composition of the surface layer has been determined. Finally, a Ca/P ratio of 1.52 was estimated from the NMR data that compares well with the value of 1.51 from chemical analysis. The important consequences are that the surface of nanocrystalline HAp has nothing in common with the bulk composition and that the chemistry of such materials (e.g. the binding of protein molecules to phosphate surfaces) must be reconsidered. Copyright © 2006 John Wiley & Sons, Ltd.
Progress in NMR: 13C of columnar liquid crystals
Progress in Nuclear Magnetic Resonance Spectroscopy
Vol: 48, Issue: 2-3, May 30, 2006
pp. 85-107
Title: Carbon-13 NMR spectroscopy applied to columnar liquid crystals
Authors: Dvinskikh, Sergey V.a, b; Sandström, Dickb; Zimmermann, Herbertc; Maliniak, Arnoldb
Affiliations: a. Institute of Physics, St Petersburg State University, Ulianovskaia 1, 198504 St Petersburg, Russian Federation
b. Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden
c. Department of Biomedical Optics, Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, D-69120 Heidelberg, Germany
Keywords: Columnar liquid crystals; Solid-state NMR; Carbon-13 NMR; Dipolar coupling; Chemical shift anisotropy
Vol: 48, Issue: 2-3, May 30, 2006
pp. 85-107
Title: Carbon-13 NMR spectroscopy applied to columnar liquid crystals
Authors: Dvinskikh, Sergey V.a, b; Sandström, Dickb; Zimmermann, Herbertc; Maliniak, Arnoldb
Affiliations: a. Institute of Physics, St Petersburg State University, Ulianovskaia 1, 198504 St Petersburg, Russian Federation
b. Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden
c. Department of Biomedical Optics, Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, D-69120 Heidelberg, Germany
Keywords: Columnar liquid crystals; Solid-state NMR; Carbon-13 NMR; Dipolar coupling; Chemical shift anisotropy
SSNMR; 19F NMR of polymers; Hazendonk
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 114-123
Title: Fluorine-19 solid state NMR study of vinylidenefluoride polymers using selective relaxation filters
Authors: Wormald, Philipa; Ameduri, Brunob; Harris, Robin K.c; Hazendonk, Pauld
Affiliations: a. School of Chemistry, University of St Andrews, Purdie Building, St. Andrews KY16 9ST, UK
b. Laboratory of Macromolecular Chemistry, Ecole Nationale de Chimie de Montpellier, Unite Mixte Recherche CNRS 5076, 8 rue de l’Ecole Normale, F 34296 Montpellier, Cedex 5, France
c. Department of Chemistry, University of Durham Science Laboratories, South Road, Durham DH1 3LE, UK
d. Department of Chemistry and Biochemistry, 4401 University Drive, University of Lethbridge, Alberta, Canada
Keywords: 19F solid-state NMR; Relaxation filters; Fluoropolymers; High-speed MAS; Vinylidene fluoride; Telomer
Abstract (English):
Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1×106 and 2×103Da by GPC, respectively, have been analysed by 19F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T1r filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to b PVDF, whereas the PVDF contained crystallites of the a form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately -115 and approximately -117ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters.
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 114-123
Title: Fluorine-19 solid state NMR study of vinylidenefluoride polymers using selective relaxation filters
Authors: Wormald, Philipa; Ameduri, Brunob; Harris, Robin K.c; Hazendonk, Pauld
Affiliations: a. School of Chemistry, University of St Andrews, Purdie Building, St. Andrews KY16 9ST, UK
b. Laboratory of Macromolecular Chemistry, Ecole Nationale de Chimie de Montpellier, Unite Mixte Recherche CNRS 5076, 8 rue de l’Ecole Normale, F 34296 Montpellier, Cedex 5, France
c. Department of Chemistry, University of Durham Science Laboratories, South Road, Durham DH1 3LE, UK
d. Department of Chemistry and Biochemistry, 4401 University Drive, University of Lethbridge, Alberta, Canada
Keywords: 19F solid-state NMR; Relaxation filters; Fluoropolymers; High-speed MAS; Vinylidene fluoride; Telomer
Abstract (English):
Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1×106 and 2×103Da by GPC, respectively, have been analysed by 19F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T1r filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to b PVDF, whereas the PVDF contained crystallites of the a form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately -115 and approximately -117ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters.
SSNMR; 17O NMR, Exchange; Zr-tungstate
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 98-105
Title: Quantitative analysis of 17O exchange and ... relaxation data: Application to zirconium tungstate
Authors: Hodgkinson, Paula; Hampson, Matthew R.a
Affiliations: a. Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK
Keywords: Solid-state; NMR; Exchange; Relaxation; O-17; Quadrupole
Abstract (English):
The theoretical basis behind a recent quantitative analysis of 17O exchange in ZrW2O8 [M.R. Hampson, J.S.O. Evans, P. Hodgkinson, J. Am. Chem. Soc. 127 (2005) 15175–15181] is set out. Despite the complexities of combining the multi-exponential relaxation of half-integer quadrupolar nuclei with chemical exchange, it is shown how magnetisation transfer experiments can be analysed to obtain estimates of absolute exchange rates. The multi-exponential relaxation is best modelled using a magnetic mechanism, i.e. the rapid Formula Not Shown relaxation observed, particularly at high temperatures, can be directly related to the relatively high degree of 17O labelling employed. The combination of the 1D EXSY results with Formula Not Shown values as a function of temperature provides exchange rates and activation barriers over a wide temperature range (40–226°C).
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 98-105
Title: Quantitative analysis of 17O exchange and ... relaxation data: Application to zirconium tungstate
Authors: Hodgkinson, Paula; Hampson, Matthew R.a
Affiliations: a. Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK
Keywords: Solid-state; NMR; Exchange; Relaxation; O-17; Quadrupole
Abstract (English):
The theoretical basis behind a recent quantitative analysis of 17O exchange in ZrW2O8 [M.R. Hampson, J.S.O. Evans, P. Hodgkinson, J. Am. Chem. Soc. 127 (2005) 15175–15181] is set out. Despite the complexities of combining the multi-exponential relaxation of half-integer quadrupolar nuclei with chemical exchange, it is shown how magnetisation transfer experiments can be analysed to obtain estimates of absolute exchange rates. The multi-exponential relaxation is best modelled using a magnetic mechanism, i.e. the rapid Formula Not Shown relaxation observed, particularly at high temperatures, can be directly related to the relatively high degree of 17O labelling employed. The combination of the 1D EXSY results with Formula Not Shown values as a function of temperature provides exchange rates and activation barriers over a wide temperature range (40–226°C).
SSNMR; 17O-enriched pyrophosphates; Freude
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 69-74
Title: Solid-state NMR studies of 17O-enriched pyrophosphates
Authors: Prochnow, Daniela; Grimmer, Arnd-Rüdigerb; Freude, Dietera
Affiliations: a. Abteilung Grenzflächenphysik, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
b. Institut für Chemie, Fachinstitut für Anorganische und Allgemeine Chemie, Humboldt-Universität zu Berlin, Rudower Chaussee 5, Haus 3.51, Berlin, Germany
Keywords: NMR; Multiple quantum MAS; Double-rotation; Inorganic phosphates; Crystalline pyrophosphates; 17O
Abstract (English):
For the first time, 17O NMR studies were performed on 17O-enriched crystalline pyrophosphates (magnesium-, sodium- and barium-pyrophosphate) by means of triple-quantum magic-angle spinning (3QMAS) and double-rotation (DOR) in the high external field of 17.6T. Oxygen atoms in bridging positions (P–OB–P) exhibit a significant higher quadrupole coupling constant compared to oxygen atoms in terminal positions (P–OT). With increasing cationic radius a higher value of the chemical shift of the terminal oxygen atoms is observed.
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 69-74
Title: Solid-state NMR studies of 17O-enriched pyrophosphates
Authors: Prochnow, Daniela; Grimmer, Arnd-Rüdigerb; Freude, Dietera
Affiliations: a. Abteilung Grenzflächenphysik, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
b. Institut für Chemie, Fachinstitut für Anorganische und Allgemeine Chemie, Humboldt-Universität zu Berlin, Rudower Chaussee 5, Haus 3.51, Berlin, Germany
Keywords: NMR; Multiple quantum MAS; Double-rotation; Inorganic phosphates; Crystalline pyrophosphates; 17O
Abstract (English):
For the first time, 17O NMR studies were performed on 17O-enriched crystalline pyrophosphates (magnesium-, sodium- and barium-pyrophosphate) by means of triple-quantum magic-angle spinning (3QMAS) and double-rotation (DOR) in the high external field of 17.6T. Oxygen atoms in bridging positions (P–OB–P) exhibit a significant higher quadrupole coupling constant compared to oxygen atoms in terminal positions (P–OT). With increasing cationic radius a higher value of the chemical shift of the terminal oxygen atoms is observed.
SSNMR: 14N NQR of sulfa drugs
Solid-State NMR:
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006
pp. 61-68
Title: 14N nuclear quadrupole resonance of some sulfa drugs
Authors: Blinc, Roberta, b; Seliger, Janeza, c; Zidansek, Aleksandera, b; Zagar, Veselkoa; Milia, Fanid; Robert, Hectore
Affiliations: a. J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
b. Jožef Stefan International Postgraduate School, Jamova 39, 1000 Ljubljana, Slovenia
c. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
d. NCSR Demokritos, Aghia Paraskevi Attikis, Athens, Greece
e. GE Security, Quantum Magnetics, Inc, 15175 Innovation Dr, San Diego, CA 92128, USA
Keywords: Polymorphs; Sulfa drugs; 14N nuclear quadrupole resonance
Abstract (English):
The 14N nuclear quadrupole double resonance spectra of different polymorphs of sulfanilamide, sulfadiazine, sulfamerazine and sulfamethazine have been measured and the 14N quadrupole coupling tensors have been determined. The obtained 14N spectra are compared with those of other sulfa drugs like sulfathiazole. It is shown that different polymorphs can be easily discriminated. The application of this technique for non-destructive analysis, polymorph determination and quality control in the production of pharmaceuticals is stressed.
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006
pp. 61-68
Title: 14N nuclear quadrupole resonance of some sulfa drugs
Authors: Blinc, Roberta, b; Seliger, Janeza, c; Zidansek, Aleksandera, b; Zagar, Veselkoa; Milia, Fanid; Robert, Hectore
Affiliations: a. J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
b. Jožef Stefan International Postgraduate School, Jamova 39, 1000 Ljubljana, Slovenia
c. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
d. NCSR Demokritos, Aghia Paraskevi Attikis, Athens, Greece
e. GE Security, Quantum Magnetics, Inc, 15175 Innovation Dr, San Diego, CA 92128, USA
Keywords: Polymorphs; Sulfa drugs; 14N nuclear quadrupole resonance
Abstract (English):
The 14N nuclear quadrupole double resonance spectra of different polymorphs of sulfanilamide, sulfadiazine, sulfamerazine and sulfamethazine have been measured and the 14N quadrupole coupling tensors have been determined. The obtained 14N spectra are compared with those of other sulfa drugs like sulfathiazole. It is shown that different polymorphs can be easily discriminated. The application of this technique for non-destructive analysis, polymorph determination and quality control in the production of pharmaceuticals is stressed.
SSNMR journal update - Rob - Vol 30, i.2 Sept. 2006
Solid-State NMR:
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006
pp. 61-68
Title: 14N nuclear quadrupole resonance of some sulfa drugs
Authors: Blinc, Roberta, b; Seliger, Janeza, c; Zidansek, Aleksandera, b; Zagar, Veselkoa; Milia, Fanid; Robert, Hectore
Affiliations: a. J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
b. Jožef Stefan International Postgraduate School, Jamova 39, 1000 Ljubljana, Slovenia
c. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
d. NCSR Demokritos, Aghia Paraskevi Attikis, Athens, Greece
e. GE Security, Quantum Magnetics, Inc, 15175 Innovation Dr, San Diego, CA 92128, USA
Keywords: Polymorphs; Sulfa drugs; 14N nuclear quadrupole resonance
Abstract (English):
The 14N nuclear quadrupole double resonance spectra of different polymorphs of sulfanilamide, sulfadiazine, sulfamerazine and sulfamethazine have been measured and the 14N quadrupole coupling tensors have been determined. The obtained 14N spectra are compared with those of other sulfa drugs like sulfathiazole. It is shown that different polymorphs can be easily discriminated. The application of this technique for non-destructive analysis, polymorph determination and quality control in the production of pharmaceuticals is stressed.
---
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 69-74
Title: Solid-state NMR studies of 17O-enriched pyrophosphates
Authors: Prochnow, Daniela; Grimmer, Arnd-Rüdigerb; Freude, Dietera
Affiliations: a. Abteilung Grenzflächenphysik, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
b. Institut für Chemie, Fachinstitut für Anorganische und Allgemeine Chemie, Humboldt-Universität zu Berlin, Rudower Chaussee 5, Haus 3.51, Berlin, Germany
Keywords: NMR; Multiple quantum MAS; Double-rotation; Inorganic phosphates; Crystalline pyrophosphates; 17O
Abstract (English):
For the first time, 17O NMR studies were performed on 17O-enriched crystalline pyrophosphates (magnesium-, sodium- and barium-pyrophosphate) by means of triple-quantum magic-angle spinning (3QMAS) and double-rotation (DOR) in the high external field of 17.6T. Oxygen atoms in bridging positions (P–OB–P) exhibit a significant higher quadrupole coupling constant compared to oxygen atoms in terminal positions (P–OT). With increasing cationic radius a higher value of the chemical shift of the terminal oxygen atoms is observed.
---
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 98-105
Title: Quantitative analysis of 17O exchange and Formula Not Shown relaxation data: Application to zirconium tungstate
Authors: Hodgkinson, Paula; Hampson, Matthew R.a
Affiliations: a. Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK
Keywords: Solid-state; NMR; Exchange; Relaxation; O-17; Quadrupole
Abstract (English):
The theoretical basis behind a recent quantitative analysis of 17O exchange in ZrW2O8 [M.R. Hampson, J.S.O. Evans, P. Hodgkinson, J. Am. Chem. Soc. 127 (2005) 15175–15181] is set out. Despite the complexities of combining the multi-exponential relaxation of half-integer quadrupolar nuclei with chemical exchange, it is shown how magnetisation transfer experiments can be analysed to obtain estimates of absolute exchange rates. The multi-exponential relaxation is best modelled using a magnetic mechanism, i.e. the rapid Formula Not Shown relaxation observed, particularly at high temperatures, can be directly related to the relatively high degree of 17O labelling employed. The combination of the 1D EXSY results with Formula Not Shown values as a function of temperature provides exchange rates and activation barriers over a wide temperature range (40–226°C).
---
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 114-123
Title: Fluorine-19 solid state NMR study of vinylidenefluoride polymers using selective relaxation filters
Authors: Wormald, Philipa; Ameduri, Brunob; Harris, Robin K.c; Hazendonk, Pauld
Affiliations: a. School of Chemistry, University of St Andrews, Purdie Building, St. Andrews KY16 9ST, UK
b. Laboratory of Macromolecular Chemistry, Ecole Nationale de Chimie de Montpellier, Unite Mixte Recherche CNRS 5076, 8 rue de l’Ecole Normale, F 34296 Montpellier, Cedex 5, France
c. Department of Chemistry, University of Durham Science Laboratories, South Road, Durham DH1 3LE, UK
d. Department of Chemistry and Biochemistry, 4401 University Drive, University of Lethbridge, Alberta, Canada
Keywords: 19F solid-state NMR; Relaxation filters; Fluoropolymers; High-speed MAS; Vinylidene fluoride; Telomer
Abstract (English):
Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1×106 and 2×103Da by GPC, respectively, have been analysed by 19F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T1r filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to b PVDF, whereas the PVDF contained crystallites of the a form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately -115 and approximately -117ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters.
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006
pp. 61-68
Title: 14N nuclear quadrupole resonance of some sulfa drugs
Authors: Blinc, Roberta, b; Seliger, Janeza, c; Zidansek, Aleksandera, b; Zagar, Veselkoa; Milia, Fanid; Robert, Hectore
Affiliations: a. J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
b. Jožef Stefan International Postgraduate School, Jamova 39, 1000 Ljubljana, Slovenia
c. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
d. NCSR Demokritos, Aghia Paraskevi Attikis, Athens, Greece
e. GE Security, Quantum Magnetics, Inc, 15175 Innovation Dr, San Diego, CA 92128, USA
Keywords: Polymorphs; Sulfa drugs; 14N nuclear quadrupole resonance
Abstract (English):
The 14N nuclear quadrupole double resonance spectra of different polymorphs of sulfanilamide, sulfadiazine, sulfamerazine and sulfamethazine have been measured and the 14N quadrupole coupling tensors have been determined. The obtained 14N spectra are compared with those of other sulfa drugs like sulfathiazole. It is shown that different polymorphs can be easily discriminated. The application of this technique for non-destructive analysis, polymorph determination and quality control in the production of pharmaceuticals is stressed.
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Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 69-74
Title: Solid-state NMR studies of 17O-enriched pyrophosphates
Authors: Prochnow, Daniela; Grimmer, Arnd-Rüdigerb; Freude, Dietera
Affiliations: a. Abteilung Grenzflächenphysik, Universität Leipzig, Linnéstr. 5, 04103 Leipzig, Germany
b. Institut für Chemie, Fachinstitut für Anorganische und Allgemeine Chemie, Humboldt-Universität zu Berlin, Rudower Chaussee 5, Haus 3.51, Berlin, Germany
Keywords: NMR; Multiple quantum MAS; Double-rotation; Inorganic phosphates; Crystalline pyrophosphates; 17O
Abstract (English):
For the first time, 17O NMR studies were performed on 17O-enriched crystalline pyrophosphates (magnesium-, sodium- and barium-pyrophosphate) by means of triple-quantum magic-angle spinning (3QMAS) and double-rotation (DOR) in the high external field of 17.6T. Oxygen atoms in bridging positions (P–OB–P) exhibit a significant higher quadrupole coupling constant compared to oxygen atoms in terminal positions (P–OT). With increasing cationic radius a higher value of the chemical shift of the terminal oxygen atoms is observed.
---
Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 98-105
Title: Quantitative analysis of 17O exchange and Formula Not Shown relaxation data: Application to zirconium tungstate
Authors: Hodgkinson, Paula; Hampson, Matthew R.a
Affiliations: a. Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK
Keywords: Solid-state; NMR; Exchange; Relaxation; O-17; Quadrupole
Abstract (English):
The theoretical basis behind a recent quantitative analysis of 17O exchange in ZrW2O8 [M.R. Hampson, J.S.O. Evans, P. Hodgkinson, J. Am. Chem. Soc. 127 (2005) 15175–15181] is set out. Despite the complexities of combining the multi-exponential relaxation of half-integer quadrupolar nuclei with chemical exchange, it is shown how magnetisation transfer experiments can be analysed to obtain estimates of absolute exchange rates. The multi-exponential relaxation is best modelled using a magnetic mechanism, i.e. the rapid Formula Not Shown relaxation observed, particularly at high temperatures, can be directly related to the relatively high degree of 17O labelling employed. The combination of the 1D EXSY results with Formula Not Shown values as a function of temperature provides exchange rates and activation barriers over a wide temperature range (40–226°C).
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Solid State Nuclear Magnetic Resonance
Vol: 30, Issue: 2, September, 2006 Bibliographic Page
pp. 114-123
Title: Fluorine-19 solid state NMR study of vinylidenefluoride polymers using selective relaxation filters
Authors: Wormald, Philipa; Ameduri, Brunob; Harris, Robin K.c; Hazendonk, Pauld
Affiliations: a. School of Chemistry, University of St Andrews, Purdie Building, St. Andrews KY16 9ST, UK
b. Laboratory of Macromolecular Chemistry, Ecole Nationale de Chimie de Montpellier, Unite Mixte Recherche CNRS 5076, 8 rue de l’Ecole Normale, F 34296 Montpellier, Cedex 5, France
c. Department of Chemistry, University of Durham Science Laboratories, South Road, Durham DH1 3LE, UK
d. Department of Chemistry and Biochemistry, 4401 University Drive, University of Lethbridge, Alberta, Canada
Keywords: 19F solid-state NMR; Relaxation filters; Fluoropolymers; High-speed MAS; Vinylidene fluoride; Telomer
Abstract (English):
Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1×106 and 2×103Da by GPC, respectively, have been analysed by 19F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T1r filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to b PVDF, whereas the PVDF contained crystallites of the a form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately -115 and approximately -117ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters.
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