CORRELATION OF CHEMICAL-BOND DIRECTIONS AND FUNCTIONAL-GROUP ORIENTATIONS IN SOLIDS BY 2-DIMENSIONAL NMR

We describe a new two-dimensional NMR technique for structural studies of polycrystalline and noncrystalline solids. The technique is a variant of 2D exchange spectroscopy applicable to organic molecules, macromolecules, or molecular complexes that are doubly 13C-labeled at a specific carboncarbon bond and singly 13C labeled at a specific functional group. A Carr-Purcell sequence is used to obtain dipolar spectra in the t1 dimension. Spectra in the t2 dimension are determined primarily by the chemical-shift anisotropy. With spin diffusion among the labeled sites between the t1 and t2 periods, the resulting 2D spectra reveal correlations between the direction of the labeled bond and the orientation of the labeled functional group. Experimental spectra of two polycrystalline model compounds, dimethyl succinate and diammonium succinate, are presented and compared with simulations to illustrate the structural information contained in the 2D spectra. © 1993 by Academic Press, Inc.