New opportunities in acquisition and analysis of natural abundance complex solid-state 33S MAS NMR spectra: (CH3NH3)2WS4

Abstract

Population transfer from the satellite transitions to the central transition in solid-state ³³S MAS NMR, employing WURST inversion pulses, has led to detection of the most complex ³³S MAS NMR spectrum observed so far. The spectrum is that of (CH₃NH₃)₂WS₄ and consists of three sets of overlapping resonances for the three non-equivalent S atoms, in accord with its crystal structure. It has been fully analyzed in terms of three sets of ³³S quadrupole coupling and anisotropic/isotropic chemical shift parameters along with their corresponding set of three Euler angles describing the relative orientation of the tensors for these two interactions. The three sets of spectral parameters have been assigned to the three different sulfur sites in (CH₃NH₃)₂WS₄ by relating the changes observed for the spectral parameters to the changes in crystal structures in a comparison with the corresponding data for the isostructural (NH₄)₂WS₄ analog.