Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5407676 | Journal of Magnetic Resonance | 2006 | 9 Pages |
Abstract
An experimental procedure for CP/MAS polarization transfer from remote 1H nuclear spins is introduced, which is applicable to protonated carbons in organic solids. It is based on preparing a state of non-uniform polarization, where directly bonded 13C-1H nuclei are de-polarized prior to recording the CP buildup curve. This curve is then expected to quantify the polarization transfer from remote protons only. The ability of the cross-polarization/polarization-inversion (CPPI) sequence to generate an initial state suitable for remote 1H CP/MAS scheme is analyzed both theoretically and experimentally. Confining to aliphatic groups, it was found that complete de-polarization of bonded proton is possible in the case of CH, whereas for CH2 and CH3 moieties only a partial de-polarization can be achieved. The theoretical predictions have been verified in practice for the particular case of l-alanine. The significance of the results from fundamental, as well as practical point of view, is also discussed. In particular, it is shown that: (i) the coherent description of polarization transfer under CP/MAS, including 1H polarization redistribution, is valid over time-scales longer than commonly assumed in many treatments of cross-polarization, and (ii) the remote protons polarization transfer curve can be used in combination with the conventional CP/MAS curve to get additional structural and dynamical information in organic systems.
Related Topics
Physical Sciences and Engineering
Chemistry
Physical and Theoretical Chemistry
Authors
Carmen Tripon, Mihaela Aluas, Xenia Filip, Claudiu Filip,