Solid-state NMR update to April 2007

Solid State Nuclear Magnetic Resonance
Volume 31, Issue 2, April 2007, Pages 100-114
doi:10.1016/j.ssnmr.2007.02.004

Simulations of molecular dynamics in solid-state NMR spectra of spin-1 nuclei including effects of CSA- and EFG-terms up to second order

Flemming H. Larsen
Department of Food Science, Quality and Technology, University of Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg, Denmark
Received 15 October 2006; revised 28 January 2007. Available online 1 March 2007.

Abstract

By numerical simulations MAS and QCPMG methods for acquiring spectra of spin-1 nuclei were compared in order to determine the most sensitive experiment for analysis of molecular dynamics. To comply with the large quadrupolar constants for 14N and the CSA reported for 6Li both of these interactions are included up to second order. For 2H and 6Li both QCPMG and single-pulse MAS experiments were suitable for dynamics studies whereas the single-pulse MAS experiment were the method of choice for investigation of 14N dynamics for CQ's larger than 750 kHz at 14.1 T. This property prohibits excitation of the 14N lineshape using either single hard or softer composite rf-pulses. Focusing on 14N it was demonstrated that the centerband lineshape is sensitive toward both off-MAS and CSA effects. In addition, excitation by real-time pulses showed that proper lineshapes corresponding to a site with a CQ of 3 MHz may be excited by a very short pulse.

Keywords: QCPMG; MAS; 2H; 6Li; 14N; Solid-state; Multiple-site jump; Molecular dynamics

Solid State Nuclear Magnetic Resonance
Volume 31, Issue 2, April 2007, Pages 63-71 Result list | previous <> next
doi:10.1016/j.ssnmr.2007.01.002

Effect of magnetic particles on NMR spectra of Murchison meteorite organic matter and a polymer-based model system

E.M. Levin, S.L. Bud’ko, J.D. Mao Y. Huang and K. Schmidt-Rohr
aAmes Laboratory DOE, Iowa State University, Ames, IA 50011-3020, USA
bDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3020, USA
cDepartment of Chemistry, Iowa State University, Ames, IA 50011-3020, USA
dDepartment of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Boulevard, Norfolk, VA 23529-0126, USA
eDepartment of Geological Sciences, Brown University, Providence, RI 02912, USA
Received 26 September 2006; revised 29 November 2006. Available online 26 January 2007.

Abstract

Organic matter from the Murchison meteorite shows pronounced spinning sidebands of the 1H MAS NMR spectrum and exhibits a large bulk magnetization of 0.75 emu/g extrapolated to 94 kOe at 300 K. By comparison with data of diamagnetic polystyrene and laponite clay mixed with ferrimagnetic γ-Fe2O3 nano-particles, we show that the spinning sidebands arise from a combination of dipolar couplings of a given 1H to magnetic particles, seen in a backscattered-electron image, and to other protons. Signal loss and significant broadening of protonated-carbon peaks in 13C MAS NMR spectra of polystyrene with Fe2O3 nano-particles is demonstrated, and implications for 13C NMR spectroscopy of Murchison meteorite are discussed.

Keywords: Solid-state nuclear magnetic resonance; Paramagnetic effect; Meteorite organic matter; Magnetic particles; 1H sidebands