C-13 NMR relaxation in neutral and charged tetra-n-alkyl compounds

NMR T1 relaxation times have been measured for 13C nuclei in the alkyl chains of symmetric tetra-n-alkylstannanes dissolved in CDCl3. The results are interpreted in terms of conformational transitions occurring in the aliphatic chains superimposed to rotational diffusion of the whole molecule. A comparison with analogous tetra-n-alkylammonium salts is performed. Differences are ascribed to changes in the overall rotational diffusion deriving from effects of charge upon formation of ion-pairs and larger aggregates.