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CP: Chemische Physik
CP 12: Spektroskopie von Molekülen und Kristallen
CP 12.8: Poster
Dienstag, 10. März 1998, 18:00–20:00, P1
Two and more interacting nuclear spins in solid compounds MxP2O7 — •Stephan Dusold, Jörg Kümmerlen, and Angelika Sebald — Bayerisches Geoinstitut, Universität Bayreuth
Investigations of isolated spin I=1/2 nuclei allow the extraction of the eigenvalues of the respective shielding tensor from 1D MAS NMR spectra in a straightforward manner - but usually there is no possibility to derive the orientation of the CSA tensors in the molecular frame. If, on the other hand, two or more spins with mutual interactions (dipolar and/or J) are present, the extraction of these eigenvalues becomes more complicated or virtually impossible owing to the homogeneous nature of the lineshapes under MAS. While the presence of homonuclear dipolar interactions affords extra- complications with spectral analysis, it also offers unique possibilities to derive orientation-dependent NMR parameters from powder NMR techniques. Within this framework it is important for many typical inorganic solids to further investigate the properties of various spin systems with respect to the question whether or not isolated spin pair approximations are justified and, if so, under which experimental conditions. Here we report on 31P NMR investigations of the P2O7 unit in two different model compounds MxP2O7 (M=Na, Cd) for which an isolated spin-pair approximation is more (Na4P2O7*10H2O) or less (Cd2P2O7) valid. Results of simple 1D MAS, 2D spin echo and spin diffusion experiments for these two types of compounds MxP2O7 will be compared and discussed.