Solid-state nuclear magnetic resonance studies at ambient and cryogenic temperatures

Abstract

The research work presented in this thesis was concentrated on the study of solid materials at ambient temperature, and the study of matrix-isolated materials at cryogenic temperatures. The first was directed to the examination of organolithium and organocopper compounds with particular interest in nuclear quadrupolar effects and their relation to molecular structure. All the compounds studied were air and moisture sensitive, which made necessary the design and construction of special rotor inserts to prevent the decomposition of these materials. A series of LiBH(_4)X(_n) compounds were studied. They showed a good correlation between the symmetry of the Li-X bonds and the quadrupole coupling constants, which allows the prediction of molecular structures for some of the complexes. The design and construction of an integrated NMR-cryogenic system was carried out for the deposition and study of matrix-isolated materials. A full description of the system and the way it is assembled is presented. A method to determine the sample temperature is introduced where the NMR signal from the deposited sample is used as a probe. CH(_2)Cl(_2) and C(_2)H(_4) in Ar matrices at different molar fractions were studied . The inter-proton distance was obtained for theCH(_2)Cl(_2) case. This work also shows a relation between the degree of isolation and the multi-exponential T(_1) behaviour.