Friday, March 31, 2006

JPCB, Raftery, pharmaceuticals: 2D PASS and DFT calculations

Hiyam, please check over thoroughly

J. Phys. Chem. B, ASAP Article 10.1021/jp056195k S1520-6106(05)06195-X

Web Release Date: March 29, 2006

Analysis of Conformational Polymorphism in Pharmaceutical Solids Using Solid-State NMR and Electronic Structure Calculations

Jay R. Smith, Weizong Xu, and Daniel Raftery*

Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907


A detailed analysis of molecular structure in three polymorphic forms of 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile is made using a combination of multidimensional solid-state NMR (SSNMR) experiments and molecular modeling via electronic structure calculations. These compounds, collectively referred to as ROY because of their red, orange, and yellow colors, share a similar molecular structure with the exception of the dihedral angle between the phenyl and thiophene rings. The ROY materials make it possible to study the influence of nearly a single degree of freedom on the associated NMR spectra. Using the 2D PASS (Antzutkin et al. J. Magn. Reson. A 1995, 115, 7) experiment, spectral editing techniques, and DFT-based calculations of the local fields, an analysis is made of the sensitivity of all carbon and nitrogen sites to changing molecular conformation. Chemical shift and dipolar coupling information obtained from these experiments vary noticeably between forms and are subsequently used to quantitatively determine aspects of molecular structure in these materials, including the coplanar angle between the phenyl and thiophene rings. The influence of motion on the methyl and nitro chemical shifts is also investigated. The accuracy of the information obtained from local field analysis and the model structure calculation demonstrates the capabilities of SSNMR as a quantitative structural method.

JACS, Yesinowski, 71Ga NMR of GaN

J. Am. Chem. Soc., ASAP Article 10.1021/ja0604865 S0002-7863(06)00486-0
Web Release Date: March 28, 2006

Distributions of Conduction Electrons as Manifested in MAS NMR of Gallium Nitride

James P. Yesinowski,* Andrew P. Purdy, Huaqiang Wu, Michael G. Spencer, Janet Hunting, and Francis J. DiSalvo

Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375, and School of Electrical & Computer Engineering and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853

A strategy is demonstrated for identifying unambiguously and characterizing quantitatively the effects of distributions of conduction electron concentrations arising from intentional or unintentional dopants in semiconductors by magic-angle spinning (MAS) NMR. The 71Ga MAS NMR spectra of a number of chemically synthesized GaN samples with no intentional doping show inhomogeneously broadened absorptions to high frequency of the main peak. These broad signals are shown, from spin-lattice relaxation time measurements as a function of shift position in a single sample, to be due to Knight shifts arising from degenerate conduction electrons. For a GaN sample with Ge as an intentional dopant at the 0.13% (wt) level, the spectrum is dramatically broadened and shifted to high frequency by up to several hundred parts per million. Analysis of the inhomogeneously broadened line shape yields a quantitative probability density function for electron carrier concentration in the bulk sample that reflects significant compositional heterogeneity due to a variety of possible sources.

JACS: 51V NMR of 67.5-kDa vanadium chloroperoxidase

J. Am. Chem. Soc., ASAP Article 10.1021/ja060480f S0002-7863(06)00480-X
Web Release Date: March 25, 2006

51V Solid-State Magic Angle Spinning NMR Spectroscopy of Vanadium Chloroperoxidase

Neela Pooransingh-Margolis, Rokus Renirie, Zulfiqar Hasan, Ron Wever, Alexander J. Vega, and Tatyana Polenova*
Contribution from the Brown Laboratories, Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, Van 't Hoff Institute for Molecular Sciences, Faculty of Science, University of Amsterdam, NieuweAchtergracht 129, 1018 WS Amsterdam, The Netherlands


We report 51V solid-state NMR spectroscopy of the 67.5-kDa vanadium chloroperoxidase, at 14.1 T. We demonstrate that, despite the low concentration of vanadium sites in the protein (one per molecule, 1 mol of vanadium spins in the entire sample), the spinning sideband manifold spanning the central and the satellite transitions is readily detectable. The quadrupolar and chemical shift anisotropy tensors have been determined by numerical simulations of the spinning sideband envelopes and the line shapes of the individual spinning sidebands corresponding to the central transition. The observed quadrupolar coupling constant CQ of 10.5 ± 1.5 MHz and chemical shift anisotropy of -520 ± 13 ppm are sensitive reporters of the geometric and electronic structure of the vanadium center. Density functional theory calculations of the NMR spectroscopic observables for an extensive series of active site models indicate that the vanadate cofactor is most likely anionic with one axial hydroxo- group and an equatorial plane consisting of one hydroxo- and two oxo- groups. The work reported in this manuscript is the first example of 51V solid-state NMR spectroscopy applied to probe the vanadium center in a protein directly. This approach yields the detailed coordination environment of the metal unavailable from other experimental measurements and is expected to be generally applicable for studies of diamagnetic vanadium sites in metalloproteins.

JPCB, Mueller, more 87Sr QCPMG NMR

J. Phys. Chem. B, ASAP Article 10.1021/jp057205k S1520-6106(05)07205-6
Web Release Date: March 24, 2006

NMR Study of Strontium Binding by a Micaceous Mineral

Geoffrey M. Bowers, Ramesh Ravella, Sridhar Komarneni, and Karl T. Mueller*
Department of Chemistry and Department of Crop and Soil Sciences, Penn State University, University Park, Pennsylvania, 16802


The nature of strontium binding by soil minerals directly affects the transport and sequestration/remediation of radioactive strontium species released from leaking high-level nuclear waste storage tanks. However, the molecular-level structure of strontium binding sites has seldom been explored in phyllosilicate minerals by direct spectroscopic means and is not well-understood. In this work, we use solid-state NMR to analyze strontium directly and indirectly in a fully strontium-exchanged synthetic mica of nominal composition Na4Mg6Al4Si4O20F4. Thermogravimetric analysis, X-ray diffraction analysis, and NMR evidence supports that heat treatment at 500 C for 4 h fully dehydrates the mica, creating a hydrogen-free interlayer. Analysis of the strontium NMR spectrum of the heat-treated mica shows a single strontium environment with a quadrupolar coupling constant of 9.02 MHz and a quadrupolar asymmetry parameter of 1.0. These quadrupolar parameters are consistent with a highly distorted and asymmetric coordination environment that would be produced by strontium cations without water in the coordination sphere bound deep within the ditrigonal holes. Evidence for at least one additional strontium environment, where proton-strontium couplings may occur, was found via a 1H-87Sr transfer of populations by double resonance NMR experiment. We conclude that the strontium cations in the proton-free interlayer are observable by 87Sr NMR and bound through electrostatic interactions as nine coordinate inner-sphere complexes sitting in the ditrigonal holes. Partially hydrated strontium cations invisible to direct 87Sr NMR are also present and located on the external mica surfaces, which are known to hydrate upon exposure to atmospheric moisture. These results demonstrate that modern pulsed NMR techniques and high fields can be used effectively to provide structural details of strontium binding by phyllosilicate minerals.

Massiot, Chem Comm, 27Al-31P through bond correlations

Joel, please check

Chemical Communications, 2006, (Advance Article)

DOI: 10.1039/b600514d
Through-bond homonuclear correlation experiments in solid-state NMR applied to quadrupolar nuclei in Al–O–P–O–Al chains
Michaël Deschamps, Franck Fayon, Valérie Montouillout and Dominique Massiot
Through-bond homonuclear correlation experiments can be realised in solids between spins of type X, separated by four chemical bonds, in X–O–Y–O–X motifs, provided a J coupling between X and Y exists: central transitions of quadrupolar 27Al spins can be correlated via the J2 scalar coupling between 27Al (X) and 31P (Y) in materials featuring Al–O–P–O–Al motifs.

Monday, March 27, 2006

Cory's journals - jan2006

I will be putting the journal articles I collected for January 2006 in their usual place on Purcell by the end of today.

Thursday, March 23, 2006

Andy: Recent NMR Papers from Chemical Physics Letters

Recent NMR Papers from Chemical Physics Letters:

Volume: 416, Issue: 1-3,
(1) Behavior of phenol (phenol-d5) on NaX zeolite as studied by 1H NMR and FT-IR techniques. Beutel, Tilman; Su, Bao-Lian pp. 51-55

Volume: 416, Issue: 4-6,
(1) Effects of strong paramagnetic interactions on solid-state deuterium NMR spectra. Mizuno, Motohiro; Itakura, Naohisa; Endo, Kazunaka pp. 358-363

Volume: 417, Issue: 1-3,
(1) A new technique for cross polarization in solid-state NMR compatible with high spinning frequencies and high magnetic fields. Peng, Weng Kung; Takeda, Kazuyuki; Kitagawa, Masahiro pp. 58-62

Volume: 417, Issue: 4-6,
(1) On the carbon-13 chemical shift tensors of bent-core mesogens. Dong, Ronald Y.; Zhang, J.; Fodor-Csorba, K. pp. 475-479

Volume: 418, Issue: 1-3,
(1) Fer expansion for effective propagators and Hamiltonians in NMR. Madhu, P.K.; Kurur, Narayanan D. pp. 235-238

Volume: 418, Issue: 4-6,
(1) Scalar relativistic correction to nucleus-independent chemical shifts of coinage-metal compounds: How does the pseudopotential approximation perform? Cle´mence Corminboeuf pp. 437-441

Volume: 419, Issue: 1-3,
(1) Anisotropic indirect nuclear spin–spin coupling in InP: 31P CP NMR study under slow MAS condition: 31P CP NMR study under slow MAS condition. Iijima, Takahiro; Hashi, Kenjiro; Goto, Atsushi; Shimizu, Tadashi; Ohki, Shinobu pp. 28-32
(2) Remarkable reduction of rf power by ATANSEMA and DATANSEMA separated local field in solid-state NMR spectroscopy. Nishimura, Katsuyuki; Naito, Akira pp. 120-124
(3) Frequency selective polarization transfer based on multiple chemical shift precession. Mou, Yun; Chan, Jerry C.C. pp. 144-148
(4) Separated local field NMR spectroscopy by windowless isotropic mixing. Dvinskikh, Sergey V.; Yamamoto, Kazutoshi; Ramamoorthy, Ayyalusamy pp. 168-173
(5) Interactions between xenon and phospholipid bicelles studied by 2H/129Xe/131Xe NMR and optical pumping of nuclear spins 2H/129Xe/131Xe NMR and optical pumping of nuclear spins. Li, Xiaoxia; Newberry, Caitlin; Saha, Indrajit; Nikolaou, Panayiotis; Whiting, Nicholas; Goodson, Boyd M. pp. 233-239

Volume: 419, Issue: 4-6,
(1) Measurement of heteronuclear dipolar couplings using a rotating frame solid-state NMR experiment. Yamamoto, Kazutoshi; Dvinskikh, Sergey V.; Ramamoorthy, Ayyalusamy pp. 533-536

Volume: 420, Issue: 4-6,
(1) 1H MAS NMR monitoring of the 13C-labeled carbon scrambling for propane in zeolite H-ZSM-5 1H MAS NMR monitoring of the 13C-labeled carbon scrambling for propane in zeolite H-ZSM-5. Stepanov, Alexander G.; Arzumanov, Sergei S.; Ernst, Horst; Freude, Dieter pp. 574-576

Organometallics, Silvio Aime, [(5-C5H5)2Fe2(CO)4] Included in -Cyclodextrin


Organometallics, ASAP Article 10.1021/om051039l S0276-7333(05)01039-3
Web Release Date: March 23, 2006

Copyright © 2006 American Chemical Society
A 13C CP/MAS NMR Study of the Structure and Dynamics of [(5-C5H5)2Fe2(CO)4] Included in -Cyclodextrin: Evidence for Terminal-Bridging Exchange in the cis Isomer

Holly C. Canuto, Admir Masic, Nicholas H. Rees, Stephen J. Heyes, Roberto Gobetto, and Silvio Aime*

Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, U.K., and Dipartimento di Chimica IFM, Università di Torino, Via P. Giuria 7, 10125 Torino, Italy

Received December 5, 2005


The novel inclusion compound of -cyclodextrin with the binuclear metal carbonyl complex (5-C5H5)2Fe2(CO)4 as guest molecule is reported. 13C CP/MAS NMR spectroscopy, in the temperature range 100 to 353 K, is used to probe the structure and dynamics of the included molecules. Specifically, below ca. 240 K evidence is presented for the existence of both cis and trans isomers of included (5-C5H5)2Fe2(CO)4. Analysis of the temperature-dependence of the NMR line shapes shows that the microenvironment provided by the -cyclodextrin cavity allows much more extensive dynamic rearrangements of the guest molecules, in comparison to pure cis- or trans-(5-C5H5)2Fe2(CO)4, for which no isomerization or bridging-terminal carbonyl exchange processes are observed in this temperature regime. Notably, even at 100 K, bridging-terminal carbonyl exchange for the included trans isomer is rapid on the exchange-broadening time scale. However, the inclusion cavity is still more dynamically restrictive than a solution environment, and the rates of various exchange processes are usefully modified compared to those detected in solution. For (5-C5H5)2Fe2(CO)4 included in -cyclodextrin, contrary to the situation found in solution, the rate of bridging-terminal carbonyl exchange in the cis isomer is greater than the rate of cis-trans isomerization; in solution direct bridging-terminal exchange in the cis isomer could not be studied because indirect exchange via isomerization to the trans form, which undergoes rapid bridging-terminal exchange, is always significantly faster. By restricting isomerization, the inclusion environment thus confirms for the first time that the cis isomer is capable of carbonyl exchange and would allow the study of its rate and activation parameters.

Hiyam's Journals

Physical Chemistry Chemical Physics, 2006, 8, 137 - 143DOI: 10.1039/b513392k
Title: Assigning carbon-13 NMR spectra to crystal structures by the INADEQUATE pulse sequence and first principles computation: a case study of two forms of testosterone

Authors: Robin K. Harris, Siân A. Joyce, Chris J. Pickard, Sylvian Cadars and Lyndon Emsley

Abstract: A 13C CPMAS NMR experiment at high field (11.7 T) has produced significantly improved dispersion for the form of testosterone, allowing revisions and extensions to be made to the assignments. Correlations shown by an INADEQUATE two-dimensional spectrum, recorded at 16.5 T, have allowed the components of most of the doublet signals to be grouped into two sets (for the two crystallographically independent molecules). First-principles computations, employing a fully solid-state approach, have been used to obtain values for the crystallographic splittings, which are discussed in relation to the experimental values. This procedure enables assignments to the two groups to be suggested for all but one of the remaining doublet signals. It also allows the two sets of signals to be identified specifically to the two independent molecules in the crystal structure. Computations were also carried out for the form of testosterone (a dihydrate). The shift differences between the and forms were compared with the experimental data, with encouraging results. Comparisons were also made between computed and experimental shielding anisotropies and asymmetries for three of the carbons of the form. The methodology has a high potential for future applications, though more examples need to be evaluated before general conclusions can be drawn.
Physical Chemistry Chemical Physics, 2006, 8, 369 - 378DOI: 10.1039/b512236h
Title: Silver ion dynamics in the Ag5Te2Cl-polymorphs revealed by solid state NMR lineshape and two- and three-time correlation spectroscopies

Authors: Christian Brinkmann, Sandra Faske, Michael Vogel, Tom Nilges, Andreas Heuer and Hellmut Eckert

Abstract: The relation between structure and ion dynamics in the three polymorphs of Ag5Te2Cl has been investigated using 109Ag, 125Te, and 35Cl NMR spectroscopies. Specifically, the influence of the structural phase transitions observed near 240 K (P21/cP21/n) and near 332 K (P21/nI4/mcm) upon silver ion mobilities has been studied by temperature dependent 109Ag NMR lineshapes and spin–lattice relaxation times. While the superionic high temperature phase -Ag5Te2Cl is characterized by a molten cationic sublattice, fast ion dynamics in the medium-temperature phase -Ag5Te2Cl occurs in spatially restricted regions comprising all the crystallographically distinct silver sites. Temperature dependent magic-angle-spinning linewidths yield an activation energy of 0.38 eV, consistent with 0.44 eV measured from dc electric conductivities. For the low-temperature -modification, results of two- and three-time 109Ag correlation spectroscopies provide a detailed insight into the nature of the silver ionic hopping motion. Temperature dependent jump rates measured by two-time correlation functions yield an activation energy Ea= 0.48 eV. 109Ag NMR three-time correlation functions indicate that the non-exponential relaxation behavior of the silver ions can be attributed to a broad distribution of jump rates rather than correlated forward–backward jumps. Nevertheless, all the silver ions are mobile down to temperatures of about 185 K.

Wednesday, March 22, 2006

Physical Chemistry Chemical Physics, 2006, 8, 1394 - 1403DOI: 10.1039/b516765e
Title: Molecular dynamics and ordering of pyridine in its cyclophosphazene inclusion compound as evaluated by solid state 2H NMR spectroscopy

Authors: Jorge A. Villanueva-Garibay and Klaus Müller

Abstract: Variable temperature 2H NMR experiments (line shape analysis, relaxation studies) were carried out on the pyridine-d5–tris-(1,2-dioxyphenyl)-cyclotriphosphazene inclusion compound in the temperature range between 110–300 K. It is found that the pyridine guests are highly mobile throughout the whole temperature range covered here. The observation of three superimposed 2H NMR signals can be understood in terms of a particular (motionally averaged) orientation of the pyridine molecules, which is a consequence of the molecular symmetry of the pyridine guests and the imposed channel restrictions. The experimental data are consistent with a combined rotation on cone–small angle fluctuation model, which assumes a fast molecular reorientation between two superimposed cones with an opening angle for the inner cone between 59–73° (angle of fluctuation between 1–3°). On the basis of this model assumption it is possible to reproduce both the experimental 2H NMR line shapes and the spin–lattice relaxation data in a quantitative way. The analysis of the partially relaxed spectra (inversion recovery experiments) yields the correlation times for this overall motional process. They follow an Arrhenius behavior from which an activation energy of 8.7 ± 0.4 kJ mol–1 is derived. The results are discussed in the framework of the published data for related systems.
Chemistry - A European JournalVolume 12, Issue 8, Pages 2139-2146

Comment: Similar to my silver project

Title: Orientational Control of Guest Molecules in an Organic Intercalation System by Host Polymer Tacticity
Shinya Oshita, Akikazu Matsumoto, Prof.


Four kinds of stereoregular poly(muconic acid)s, which are synthesized by topochemical polymerization and subsequent solid-state hydrolysis, are used as the organic host materials for intercalation. We describe the reaction behavior and layered structure of intercalation compounds using stereoregular poly(muconic acid)s and n-alkylamines as host and guest, respectively. The packing structure of the guest alkylamines was determined by X-ray diffractions as well as IR and Raman spectroscopies. We have found that the orientation of the guest molecules is controlled by the host polymer tacticity, depending on the structure of the two-dimensional hydrogen-bonding network formed in the polymer sheets of the crystals.

Chemistry - A European JournalVolume 12, Issue 4, Pages 1036-1045

Comment: Sn-119 NMR

Ruthenium Complexes with the Stanna-closo-dodecaborate Ligand: Coexistence of 1(Sn) and 3(BH) Coordination
Torben Gädt , Beatrice Grau , Klaus Eichele , Ingo Pantenburg , Lars Wesemann, Prof. Dr.

Four stanna-closo-dodecaborate complexes of ruthenium have been prepared and characterized by multinuclear NMR studies in solution and in the solid state. The solid-state structures of the dimeric zwitterions [{Ru(dppb)(SnB11H11)}2] (2) (dppb=bis(diphenylphosphino)butane), [{Ru(PPh3)2(SnB11H11)}2] (3), and the dianionic ruthenium complex [Bu3MeN]2[Ru(dppb){2,7,8-(-H)3-exo-SnB11H11}(SnB11H11)] (4) were determined by X-ray crystal structure analysis; they establish an unprecedented structural motif in the chemistry of heteroboranes and transition-metal fragments with the stanna-closo-dodecaborate moiety as a two-faced ligand that exhibits 1(Sn) as well as 3(BH) coordination. The 3-coordinated stannaborate in 4 and in the isostructural compound [Bu3MeN]2[Ru(PPh3)2{2,7,8-(-H)3-exo-SnB11H11}(SnB11H11)] (5) shows fluxional behavior, which was studied in detail by using 31P{1H} EXSY and DNMR experiments. The activation parameters for the dynamic process of 5 are given.

Chemistry - A European JournalVolume 12, Issue 7, Pages 1997-2008
Comment: p-31 NMR

Title: Silver Complexes of Cyclic Hexachlorotriphosphazene Marcin Gonsior, Dr., Sasa Antonijevic, Dr., Ingo Krossing, Prof.


The first solid-state structures of complexed P3N3X6 (X=halogen) are reported for X=Cl. The compounds were obtained from P3N3Cl6 and Ag[Al(OR)4] salts in CH2Cl2/CS2 solution. The very weakly coordinating anion with R=C(CF3)3 led to the salt Ag(P3N3Cl6)2+[Al(OR)4]- (1), but the more strongly coordinating anion with R=C(CH3)(CF3)2 gave the molecular adduct (P3N3Cl6)AgAl(OR)4 (3). Crystals of [Ag(CH2Cl2)(P3N3Cl6)2]+[Al(OR)4]- (2), in which Ag+ is coordinated by two phosphazene and one CH2Cl2 ligands, were isolated from CH2Cl2 solution. The three compounds were characterized by their X-ray structures, and 1 and 3 also by NMR and vibrational spectroscopy. Solution and solid-state 31P NMR investigations in combination with quantum chemically calculated chemical shifts show that the 31P NMR shifts of free and silver-coordinated P3N3Cl6 differ by less than 3 ppm and indicate a very weakly bound P3N3Cl6 ligand in 1. The experimental silver ion affinity (SIA) of the phosphazene ligand was derived from the solid-state structure of 3. The SIA shows that (PNCl2)3 is only a slightly stronger Lewis base than P4 and CH2Cl2, while other ligands such as S8, P4S3, toluene, and 1,2-Cl2C2H4 are far stronger ligands towards the silver cation. The energetics of the complexes were assessed with inclusion of entropic, thermal, and solvation contributions (MP2/TZVPP, COSMO). The formation of the cations in 1, 2, and 3 was calculated to be exergonic by rG°(CH2Cl2)=-97, -107, and -27 kJ mol-1, respectively. All prepared complexes are thermally stable; formation of P3N3Cl5+ and AgCl was not observed, even at 60 °C in an ultrasonic bath. Therefore, the formation of P3N3Cl5+ was investigated by quantum chemical calculations. Other possible reaction pathways that could lead to the successful preparation of P3N3X5+ salts were defined.

Tuesday, March 21, 2006

Joel's Journal Update

Similar to Cory, I have added my journals to the same folder he created on Purcell. I have also made a new folder for the articles from the beginning of January to March 7, 2006. In the main folder, i have added files containing the usual article information (title, author, abstract etc.) for all of the journal articles that I have collected. You can have a glance at these and see what may be of interest to you (I've put names to the articles to whom it may be most relevant to). But for now, here are a few articles that some of you may be interested in from 2006.

Nanopatterning and Nanochange Writing in Layer-by-Layer Quinquethiophene/Phthalocyanine Ultrathin Films.
A. Baba, J. Locklin, R.S. Xu, R. Advincula
J.Phys.Chem.B (2006)110, 24.

Nanometer-scale patterning and charging in layer-by-layer (LbL) ultrathin films of quinquethiophene (5TN)/ phthalocyanine (CuPS) provides a novel write-read device using a standard current-sensing atomic force microscopy (CS-AFM). The AFM height images showed dented or raised morphological features that could be selectively manipulated by changing the direction of the bias voltages. The conductivity was repeatedly changed between a conductive and insulating state, originating from an electrochemical charging-discharging effect. This was attributed to electrochemical ion transport and the residual mobile ions present in LbL films. Finally, the nanocharge pattern was written by CS-AFM and read out in a conductivity map image.

Ultrafast Excitation Dynamics in CdSe Quantum Dots Studied from Bleaching Recovery and Fluorescence Transients.
H. Wang, C. De Donega, A. Meijerink, M. Glasbeek.
J.Phys.Chem.B (2006)110, 733.

We have performed ultrafast absorption bleach recovery and fluorescence upconversion measurements (~100 fs time resolution) for three CdSe samples, with nanoparticle diameters of 2.7, 2.9, and 4.3 nm. The two types of experiments provide complementary information regarding the contributions of the different processes involved in the fast relaxation of electrons and holes in the CdSe quantum dots. Transient absorption and emission experiments were conducted for the 1S [1S(e) - 1S3/2(h)] transition, S(e) and 1S3/2(h) representing the lowest electron (e) and hole (h) levels. The bleach recovery of the 1S transition shows a ~400-500 fs initial rise, which is followed by a size-dependent ~10-90 ps decay and finally a long-lived (~ns) decay. The fluorescence upconversion signal for the 1S transition shows quite different temporal behavior: a two times slower rise time (~700-1000 fs) and, when the fluorescence upconversion signal has risen to about 20% of its maximum intensity, the signal displays a slight leveling off (bend), followed by a continued rise until the maximum intensity is reached. This bend is well reproducible and power and concentration independent. Simulations show that the bend in the rise is caused by a very fast decay component with a typical time of about 230-430 fs. Considering that the 1S quantum dot excitation is comprised of five exciton substates (F =±2, ±1L, 0L, ±1U, and 0U), we attribute the disparity in the rise of the bleaching and emission transients to the results from the dynamics of the different excitons involved in respectively the bleaching and fluorescence experiments. More specifically, in transient absorption, population changes of the F =±1U excitons are probed, in mission population effects for the F =±2 ("dark") and the F =±1L ("bright") exciton states are monitored. It is discussed that the fast (~400-500 fs) rise of the bleach recovery is representative of the feeding of the F =±1U exciton (by filling of the 1S(e) electron level) and that the slower (~700-1000 fs) feeding of the emissive ±2, ±1L excitons is determined by the relaxation of the hole levels within the 1S3/2 fine structure. Finally, the ~230-430 fs component, typical of the bend in the fluorescence transient, is attributed to the thermalization of the close-lying ±2 ("dark") and ±1L ("bright") excitons.

Preparation and Third-Order Optical Nonlinearity of Self-Assembled Chitosan/CdSe-ZnS Core-Shell Quantum Dots Multilayer Films.
X. Wang, Y. Du, S. Ding, Q. Wang, G. Xiong, M. Xie, X. Shen, D. Pang
J.Phys.Chem.B (2006)110, 1566.

The self-assembed chitosan CdSe quantum dots (QDs) and chitosan CdSe-ZnS core-shell QDs films have been prepared by using layer-by-layer electrostatic technique. The well-ordered nanostructure and the layerby- layer deposition of the QDs are revealed by AFM and exciton absorption spectra, respectively. The optical nonlinearity of the composite films were studied by using Z-scan technique with femtosecond pulses at the wavelength of 790 nm, the value of third-order susceptibility of core-shell QDs are measured to be about 1.1 ×10-8 esu, which is about 200% larger than that of CdSe QDs of 5.3×10-9 esu. This has potential applications in all-optical switches in optical information processing.

Two-Dimensional Crystal Growth and Stacking of Bis(phthalocyaninato) Rare Earth Sandwich Complexes as the 1-Phenyloctane/Graphite Interphace.
T. Takami, D.P. Arnold, A.V. Fuchs, G.D. Will, R. Goh, E.R. Waclawik, J.M. Bell, P.S. Weiss, K. Sugiura, W. Liu, J. Jiang.
J.Phys.Chem.B (2006)110, 1661.

Initial stages of two-dimensional crystal growth of the double-decker sandwich complex Lu(Pc*)2 [Pc* ) 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] have been studied by scanning tunneling microscopy at the liquid/solid interface between 1-phenyloctane and highly oriented pyrolytic graphite. High-resolution images strongly suggest alignment of the double-decker molecules into monolayers with the phthalocyanine rings parallel to the surface. Domains were observed with either hexagonal or quadrate packing motifs, and the growing interface of the layer was imaged. Molecular resolution was achieved, and the face of the phthalocyanine rings appeared as somewhat diffuse circular features. The alkyl chains are proposed to be interdigitating to maintain planar side-by-side packing.

Communication: Conducting-Polymer Nanotubes for Controlled Drug Release
M.R. Abidian, D.H. Kim, D.C. Martin
Advan. Mat. (2006)18, 405.

Controlled release of an anti-inflammatory drug from PEDOT nanotubes using electrical stimulation is demonstrated (see Figure and Inside Cover). The fabrication process includes electrospinning of a biodegradable polymer into which the drug has been incorporated, followed by electrochemical deposition of the conducting polymer around the drug-loaded electrospun nanoscale fibers.

Pentaporphyrin as a Switching Device Activated by Proton and Redox Stimuli.
P. Ceroni, G. Bergamini, N. Aubert, V. Troiani and N. Solladie.
ChemPhysChem (2005) 10, 2120.

The authors investigate the electron charge transfer capabilities of a metalloporphyrin. The porphyrin of interest contains a peptidic backbone with flexible peptidic spacers having either PH2, PZn and PMg on the end (see pic). The aim is to determine if the electron transfer is efficient and if the emission can be controlled by electron or chemical stimuli. What they found was that the the light emitted can be tuned by protonation of the free-base unit and that it can be turned off by a redox in put which quenches the free-base porphyrin emission.

(Kurt's Paper on Fuel Cells if anyone's interested)
The Use of 1H NMR Microscopy to Study Proton-Exchange Membrane Fuel Cells
K.W. Feindel, S.H. Bergens, R.E. Wasylishen
ChemPhysChem (2006) 7(1), 67.

To understand proton-exchange membrane fuel cells (PEMFCs) better, researchers have used several techniques to visualize their internal operation. This Concept outlines the advantages of using 1H NMR microscopy, that is, magnetic resonance imaging, to monitor the distribution of water in a working PEMFC. We describe what a PEMFC is, how it operates, and why monitoring water distribution in a fuel cell is important. We will focus on our experience in constructing PEMFCs, and demonstrate how 1H NMR microscopy is used to observe the water distribution throughout an operating hydrogen PEMFC. Research in this area is briefly reviewed, followed by some comments regarding challenges and anticipated future developments.

Monday, March 20, 2006

Cory's journals sept05-dec05

All the journal articles I collected from sept/05 (last group meeting) until dec/05 (start of this blog) will be placed in their usual place on Purcell (don't want to get too specific here...) by the end of today.

Just to remind you guys, I'm responsible for:

- J. Am. Chem. Soc.
- J. Mat. Chem.
- Angew. Chem. Int.
- Phys. Rev. Lett.


JPCB: Goward, 7Li NMR, EXSY, Li3V2(PO4)3, fast MAS

J. Phys. Chem. B, ASAP Article 10.1021/jp057015+ S1520-6106(05)07015-X
Web Release Date: March 17, 2006

7Li NMR and Two-Dimensional Exchange Study of Lithium Dynamics in Monoclinic Li3V2(PO4)3

L. S. Cahill, R. P. Chapman, J. F. Britten, and G. R. Goward*

Department of Chemistry and Brockhouse Institute for Materials Research, McMaster University, 1280 Main Street W., Hamilton, ON, L8S 4M1 Canada


High-resolution solid-state 7Li NMR was used to characterize the structure and dynamics of lithium ion transport in monoclinic Li3V2(PO4)3. Under fast magic-angle spinning (MAS) conditions (25 kHz), three resonances are clearly resolved and assigned to the three unique crystallographic sites. This assignment is based on the Fermi-contact delocalization interaction between the unpaired d-electrons at the vanadium centers and the lithium ions. One-dimensional variable-temperature NMR and two-dimensional exchange spectroscopy (EXSY) are used to probe Li mobility between the three sites. Very fast exchange, on the microsecond time scale, was observed for the Li hopping processes. Activation energies are determined and correlated to structural properties including interatomic Li distances and Li-O bottleneck sizes.

JPCB, van Eck, 27Al-13C NMR of alkoxides

J. Phys. Chem. B, ASAP Article 10.1021/jp055058k S1520-6106(05)05058-3
Web Release Date: March 15, 2006

Multinuclear Solid-State High-Resolution and13C -{27Al} Double-Resonance Magic-Angle Spinning NMR Studies on Aluminum Alkoxides

Anuji Abraham, Roel Prins, and Jeroen A. van Bokhoven*

Institute for Chemical and Bioengineering, Swiss Federal Institute of Technology (ETH), Zurich 8093, Switzerland

Ernst R. H. van Eck* and Arno P. M. Kentgens

Department of Physical Chemistry - Solid-State NMR, Institute for Molecules and Materials, Radboud University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, Netherlands


A combination of 27Al magic-angle spinning (MAS)/multiple quantum (MQ)-MAS, 13C-1H CPMAS, and 13C-{27Al} transfer of population in double-resonance (TRAPDOR) nuclear magnetic resonance (NMR) were used for the structural elucidation of the aluminum alkoxides aluminum ethoxide, aluminum isopropoxide, and aluminum tertiarybutoxide. Aluminum alkoxides exist as oligomers with aluminum in different coordinations. High-resolution 27Al MAS NMR experiments with high-spinning speed distinguished the aluminum atoms in different environments. The 27Al MAS NMR spectrum gave well-resolved powder patterns with different coordinations. Z-filter MQ-MAS was performed to obtain the number and types of aluminum environments in the oligomeric structure. 13C-1H CPMAS chemical shifts resolved the different carbon species (-CH3, =CH2, =CH-, and =C=) in the structures. 13C-{27Al} TRAPDOR experiments were employed to obtain relative Al-C dipolar interactions and to distinguish between terminal and bridging alkoxides in the crystallographic structures. The complete characterization of selected aluminum alkoxides using advanced NMR methods has evidenced the tetrameric structure for aluminum isopropoxide and the dimeric structure for aluminum tertiary-butoxide, as reported in the literature, and proposed a polymeric structure for aluminum ethoxide.

Sunday, March 19, 2006

CPL, M.E. Smith et al., 17O NMR; high-res

Enhancing resolution and sensitivity of 17O solid-state NMR through combining double rotation, 1H decoupling and satellite modulation for biomolecular applications

A.P. Howes, T. Anupõld, V. Lemaitre, A. Kukol, A. Watts, A. Samoson, M.E. Smith and R. Dupree

Department of Physics, University of Warwick, Coventry CV4 7AL, UK


17O solid-state NMR is a highly sensitive probe of structural detail of organic solids but improvements in sensitivity and resolution are crucial for it to be applied to larger biological molecules. Here it is shown that high resolution (not, vert, similar1 ppm) and significant signal enhancement can be achieved by combining 1H decoupled double rotation (DOR), which narrows the lines by a factor of not, vert, similar100 compared to conventional magic angle spinning, and manipulation of the satellite transition populations to transfer magnetisation to the central transition, which produces a signal enhancement of not, vert, similar.

Thursday, March 16, 2006

Chem Mater:Effect of Sodium Doping in -Tricalcium Phosphate on Its Structure and Propertie

- 31P-23Na REDOR experiments

Chem. Mater., 18 (6), 1425 -1433, 20

Effect of Sodium Doping in -Tricalcium Phosphate on Its Structure and Properties
Laetitia Obadia, Philippe Deniard, Bruno Alonso, Thierry Rouillon, Stéphane Jobic, Jérôme Guicheux, Marion Julien, Dominique Massiot, Bruno Bujoli,* and Jean-Michel Bouler

Abstract: For the preparation of -TCP and biphasic calcium phosphates (BCPs, mixtures of hydroxyapatite and -TCP), the presence of sodium in the reaction medium results in the incorporation of sodium in the -TCP network, by substitution of some calcium sites. Accordingly, a decrease of the unit cell volume of -TCP was observed with increasing sodium substitution. The distribution of sodium in the -TCP structure, as a function of the amount incorporated, was probed using 31P and 23Na MAS NMR and 31P{23Na} REDOR experiments. It was shown that an estimation of the sodium content in -TCPs could be obtained from the modeling of their 31P MAS NMR spectra. Moreover, the incorporation of sodium in -TCPs results in improved mechanical properties, without affecting the biocompatibility of the ceramics.

Inorg Chem: Acetylenic Carbon-13 Chemical Shift Tensors for Diphenylacetylene and (2-Diphenylacetylene)Pt(PPh3)2: A Solid-State NMR and Theoretical St

- A Rod paper. Looks like its related to Cory's work.

Inorg. Chem., 45 (6), 2461 -2473, 2006

Acetylenic Carbon-13 Chemical Shift Tensors for Diphenylacetylene and (2-Diphenylacetylene)Pt(PPh3)2: A Solid-State NMR and Theoretical Study
Kristopher J. Harris, Guy M. Bernard, Chris McDonald, Robert McDonald, Michael J. Ferguson, and Roderick E. Wasylishen*
Department of Chemistry and X-ray Crystallography Laboratory, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
Received September 9, 2005

Abstract: The structure of (2-diphenylacetylene)Pt(PPh3) 2, as well as those of its dichloromethane and benzene solvates, is determined via X-ray crystallography. An investigation of the chemical shift (CS) tensors of the 13C-labeled carbons in Ph13C13CPh and (2-Ph13C13CPh)Pt(PPh3)2·(C6H6) is carried out via analysis of 13C NMR spectra from stationary solid samples. The principal components of the CS tensors as well as their orientations with respect to the 13C,13C internuclear vector are determined. DFT calculations of these CS tensors are in close agreement with the experimental values. For diphenylacetylene (tolane), the orientations and principal-component magnitudes of the alkynyl carbon CS tensors are comparable to those for other alkynyl carbons, although the CS tensor is not axially symmetric in this case. Coordination to platinum causes a change in the CS tensor orientation and a net increase in the isotropic chemical shift, resulting from a significant increase in two principal components (11 and 33) while the third (22) decreases only slightly. The measured carbon CS tensors in the platinum complex bear a striking similarity to those of the alkenyl carbons in trans-Ph(H)C=C(H)Ph, and a short theoretical discussion of these observations is presented.

Inorg Chem: Large Pressure-Induced Red Shift of the Luminescence Band Originating from Nonstacked Square-Planar [Pt(SCN)4]2- in a Novel Trimetallic C

- Possible application of Pt NMR??

Inorg. Chem., 45 (6), 2379 -2381, 2006

Large Pressure-Induced Red Shift of the Luminescence Band Originating from Nonstacked Square-Planar [Pt(SCN)4]2- in a Novel Trimetallic Complex
Geneviève Levasseur-Thériault, Christian Reber,* Christophe Aronica, and Dominique Luneau*
Département de Chimie, Université de Montréal, Montréal, Québec H3C 3J7, Canada, and Laboratoire des Multimatériaux et Interfaces (UMR 5615), Université Claude Bernard Lyon 1, Campus de La Doua, 69622 Villeurbanne Cedex, France
Received October 24, 2005

Abstract: Luminescence of the novel trimetallic complex {Pt(SCN)2[(-SCN)Mn(NCS)(bipy)2]2} originates from a d-d transition of the square-planar [Pt(SCN)4]2- moiety. The band maximum shows a red shift of -99 cm-1 kbar-1 under external pressure up to 32 kbar at room temperature. This red shift is comparable to values for crystals where Pt-Pt interaction between stacked complexes is enhanced by pressure, but the crystal structure for the trimetallic complex shows that no metal-metal interaction can occur.

Inorg Chem:Investigation of Vanadocene(IV) -Amino Acid Complexes: Synthesis, Structure, and Behavior in Physiological Solutions, Human Plasma, and Blo

- Study of a vanadocene and its behaviour in plasma like solutions. The vanadocene supposedley has applications as a cancer drug.

Inorg. Chem., 45 (5), 2156 -2162, 2006

Investigation of Vanadocene(IV) -Amino Acid Complexes: Synthesis, Structure, and Behavior in Physiological Solutions, Human Plasma, and Blood
Jaromír Vinklárek,* Hana Paláková, Jan Honzíek, Jana Holubová, Michal Holapek, and Ivana Císaová
Department of General and Inorganic Chemistry, University of Pardubice, nám. s. legií 565, 532 10 Pardubice, Czech Republic, Department of Analytical Chemistry, University of Pardubice, nám. s. legií 565, 532 10 Pardubice, Czech Republic, and Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
Received May 3, 2005

Abstract: This work is focused on investigating the interaction of antitumor active metallocene vanadocene dichloride (Cp2VCl2) and amino acids in aqueous solution at physiological pH. Sixteen vanadocene amino acid complexes [Cp2V(aa)][X] (aa = gly, ala, val, leu, ile, phe, his, and trp; X = Cl, PF6) were prepared and characterized on the basis of spectral measurements (EPR, MS, IR, Raman). Amino acids are coordinated to the vanadocene fragment through the oxygen atom of the carboxylic group and the nitrogen of the amino group, resulting in a five-membered chelate ring. Complexes [Cp2V(val)][PF6] and [Cp2V(ile)][PF6] have been characterized by X-ray structure analyses. It was evidenced that all prepared complexes are stable in both aqueous solutions with physiological pH and in therapeutic NaCl solutions. EPR spectra of vanadocene amino acid complexes in Krebs-Ringer solution in human blood plasma and in whole blood showed that these complexes react with the hydrogen carbonate anion present forming complex Cp2V(O2CO).

Thursday, March 09, 2006

Chem. Comm.: 129Xe NMR; microporosity of clays

Chemical Communications, 2006, (Advance Article)
DOI: 10.1039/b602040b

Nanoporosity of an organo-clay shown by hyperpolarized xenon and 2D NMR spectroscopy

Piero Sozzani, Silvia Bracco, Angiolina Comotti, Michele Mauri, Roberto Simonutti and Patrizia Valsesia

Interlayer nanoporosity of hectorite pillared by tetraethylammonium ions is explored by hyperpolarized xenon NMR and relevant gases such as carbon dioxide revealing the adsorption capacity of the open galleries.

JACS: 13C CP/MAS NMR : isomers of tris(8-hydroxyquinoline) aluminum(III)

J. Am. Chem. Soc., ASAP Article 10.1021/ja0565774 S0002-7863(05)06577-7
Web Release Date: March 9, 2006

CP/MAS 13C NMR Characterization of the Isomeric States and Intermolecular Packing in Tris(8-hydroxyquinoline) Aluminum(III) (Alq3)

Hironori Kaji,* Yasunari Kusaka, Goro Onoyama, and Fumitaka Horii

Contribution from the Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan, and PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan


The isomeric states and intermolecular packing of tris(8-hydroxyquinoline) aluminum(III) (Alq3) in the -, -, and -crystalline forms and in the amorphous state, which are important for understanding the light-emitting and electron-transport properties, have been analyzed by CP/MAS 13C NMR. This simple NMR experiment shows that the isomeric state of - and amorphous Alq3 is meridional, whereas that of - and -Alq3 is facial. In the amorphous Alq3, the inclusion of facial isomers has been under debate. Our experiments show that meridional isomers are dominant in the amorphous Alq3, although the existence of facial isomers cannot be completely denied. The local structure of amorphous Alq3 is similar to that of -Alq3 and is significantly different from those of - and -Alq3. Among these Alq3 samples, the effect of intermolecular interaction is not found only for -Alq3. This finding can explain the good solvent solubility of -Alq3, compared with the other crystalline forms. It is also shown that the structures are locally disordered not only for amorphous Alq3 but also for -Alq3, although clear X-ray diffraction peaks are observed for -Alq3. In contrast, the local structures of - and -Alq3 are well defined. A clear relation is found between the spectral patterns of CP/MAS 13C NMR and the fluorescence wavelengths; the samples, which consist of facial isomers, show blue-shifted fluorescence compared with those of meridionals.

Eurr. J. Inorg. Chem.: Austenbach: DFT/ZORA 183W and 17O

European Journal of Inorganic Chemistry
Volume 2006, Issue 6 , Pages 1139 - 1148

Density-Functional Calculation of the 183W and 17O NMR Chemical Shifts for Large Polyoxotungstates
Jose Gracia 1, Josep M. Poblet 1 *, Jochen Autschbach 3, Leonid P. Kazansky 2 *

Density-functional calculations • NMR spectroscopy • Tungsten • Oxygen • Polyoxometalates

A phosphane sulfate relativistic DFT method (ZORA)has been used to calculate the 183W and 17O NMR chemicalshifts for large polyoxotungstates, including W6O192-,CH3OTiW5O183-, W5O18WIINO3-, W10O324-, ---XW12O40n-, -PW9O28Br63-, P2W18O626-, PW2O143-, and W7O246-, based on their optimized molecular structures. Despite sizeable deviations between the calculated and experimental values, the calculations correctly reproduce the trends in the change of the chemical shift for both nuclei. As expected, the diamagnetic term is almost constant throughout the whole series. The change in the chemical shifts is shown to be determined by the paramagnetic term, which depends on the electronic structure of the whole anion under study and, in particular, on the local geometry around a given tungsten atom. On the other hand, there is no correlation between the chemical shift and HOMO-LUMO gap, showing that deeper occupied levels and several unoccupied orbitals play an important role in the paramagnetic term. However, analysis of the components of the paramagnetic shielding has shown that the most significant transitions determining the change of both 183W and 17O NMR chemical shifts for anions consisting of tungsten and oxygen atoms are the occupied-occupied and not the occupied-virtual ones.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Wednesday, March 08, 2006

CPL: Freude: 1H MAS NMR/ propane in zeolite ZSM5

Chemical Physics Letters
Volume 420, Issues 4-6 , 21 March 2006, Pages 574-576

1H MAS NMR monitoring of the 13C-labeled carbon scrambling for propane
in zeolite H-ZSM-5

Alexander G. Stepanova, Corresponding Author Contact Information, E-mail
The Corresponding Author, Sergei S. Arzumanova, Horst Ernstb and Dieter

Received 19 October 2005. Available online 2 February 2006.


It has been demonstrated that 1H MAS NMR spectroscopy can be used as a
tool for in situ monitoring the reaction kinetics of 13C-labeled carbon
scrambling in alkane molecules adsorbed on zeolite catalysts at the
reaction temperature of 540–570 K. The accuracy of the results and the
time resolution are improved compared to 13C MAS NMR spectroscopy.

Thursday, March 02, 2006


J. Am. Chem. Soc., ASAP Article 10.1021/ja057347s S0002-7863(05)07347-6
Web Release Date: March 2, 2006

Observation of Solid-State 103Rh NMR by Cross-Polarization

Brian L. Phillips,* Jacqueline R. Houston, Jian Feng, and William H. Casey

Center for Environmental Molecular Science, Departments of Geosciences and Chemistry, State University of New York, Stony Brook, New York 11794, and Department of Chemistry, University of California, Davis, California 95616


Using 103Rh[1H] cross-polarization (CP) methods, we have obtained solid-state 103Rh NMR spectra for diamagnetic Rh(III) compounds. The isotropic chemical shift and chemical shift anisotropy (CSA) are reported for a crystalline form of the dihydroxy-bridged Rh(III) dimer and for a salt of the oxo-centered acetate-bridged Rh(III) trimer, from analysis of conventional CP/MAS spectra. Comparison of the CP kinetics of the dimer with new crystal structure data suggests a strategy for predicting 103Rh CP/MAS properties in solids.