Guerry, Paul and Smith, Mark E. and Brown, Steven P. (2009) P-31 MAS refocused INADEQUATE spin-echo (REINE) NMR spectroscopy : revealing J coupling and chemical shift two-dimensional correlations in disordered solids. Journal of the American Chemical Society, 131 (33). pp. 11861-11874.Full text not available from this repository.
Two-dimensional (2D) variations in (2)J(P1,P1), (2)J(P1,P2), and (2)J(P2,P2) are obtained-using the REINE (REfocused INADEQUATE spin-Echo) pulse sequence presented by Cadars et al. (Phys. Chem. Chem. Phys. 2007, 9, 92-103)-from pixel-by-pixel fittings of the spin-echo modulation for the 2D correlation peaks due to linked phosphate tetrahedra (P-1-P-1, P-1-P-2, P-2-P-1, and P-2-P-2) in a P-31 refocused INADEQUATE solid-state MAS NMR spectrum of a cadmium phosphate glass, 0.575CdO-0.425P(2)O(5). In particular, separate variations for each 2D P-31 REINE peak are obtained which reveal correlations between the J couplings and the P-31 chemical shifts of the coupled nuclei that are much clearer than those evident in previously presented 2D z-filtered P-31 spin-echo spectra. Notably, such correlations between the J couplings and the P-31 chemical shifts are observed even though the conditional probability distributions extracted using the protocol of Cadars et al. (J. Am. Chem. Soc. 2005, 127, 4466-4476) indicate that theme is no marked correlation between the P-31 chemical shifts of neighboring phosphate tetrahedra. For 2D peaks at the P-2 P-31 chemical shift in the direct dimension, there can be contributions from chains of three units (P-1-P-2-P-1), chains of four units (P-1-P-2-P-2-P-1), or longer chains or rings (-P-2-P-2-P-2-): for the representative glass considered here, best fits are obtained assuming a glass comprised predominantly of chains of four units. The following variations are found: (2)J(P1,P1) = 13.4 +/- 0.3 to 14.8 +/- 0.5 Hz, (2)J(P1,P2) = 15.0 +/- 0.3 to 18.2 +/- 0.3 Hz, and (2)J(P2,P2) = 5.9 +/- 0.6 to 9.1 +/- 0.9 Hz from the fits to the P-1-P-1, P-1-P-2, and P-2-P-2 peaks, respectively. The correlation of a particular J coupling with the P-31 chemical shifts of the considered nucleus and the coupled nucleus is quantified by the coefficients C-F2 and C-F1 that correspond to the average pixel-by-pixel change in the J coupling with respect to the chemical shift of the observed (F-2) and neighboring (F-1) P-31 nuclei, respectively.
|Journal or Publication Title:||Journal of the American Chemical Society|
|Uncontrolled Keywords:||DOUBLE-QUANTUM NMR ; INTERMEDIATE-RANGE ORDER ; SODIUM BOROPHOSPHATE GLASSES ; PHOSPHATE-BASED GLASSES ; C-13-C-13 J-COUPLINGS ; X-RAY-DIFFRACTION ; STATE NMR ; STRUCTURAL-CHARACTERIZATION ; BIOMEDICAL APPLICATIONS ; SCALAR COUPLINGS|
|Deposited On:||28 Feb 2012 11:21|
|Last Modified:||26 Jul 2012 20:10|
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