Relayed anisotropy correlation NMR: determination of dihedral angles in solids

A two-dimensional solid-state NMR method is proposed for determining the mutual orientation of the two interaction tensors in each of which a different chemical group participates, from which information on the dihedral angle can be extracted. The two-dimensional powder pattern was observed for 1,2-13C-labeled DL-alanine as a demonstration, correlating the 13C1 chemical shift anisotropy and the 13C21H dipolar coupling via polarization transfer. The OC1C2H dihedral angle as well as the orientation of the 13C1 chemical shift tensor were determined from the spectrum.