NMR relaxation study of tetrapentylammonium ions in acetonitrile solutions

Abstract

NMR measurements of the spin-lattice relaxation rates of the 'H, 13C, and 14N nuclei and spin-echo self-diffusion coefficients are reported for tetrapentylammonium bromide in acetonitrile solutions Over a wide range of temperatures and concentrations. The results are discussed in terms of overall and segmental motions of the aliphatic chains of the organic ions. Order parameters characterizing the geometrical constraints upon local segmental motions are given also. Cationic self-diffusion coefficients are found to differ from those obtained with quasi-elastic neutron scattering techniques (QENS). The difference may be explained in terms of fast and slow modes contributing to the diffusion processes and their selective detection with QENS and NMR techniques.

Multinuclear high‐pressure NMR investigations of undercooled aqueous solutions of hydrophobic ions

“…Certainly the coordinated water molecules do not move with the apolar cations over appreciable distances corresponding roughly to one ionic diameter. Hence exchange of water molecules between neighboring hydration shells (radial diffUsion) must occur frequently and lateral diffusion over appreciable time scales seems to be less fa-Interesting new information might be obtained from a comparison of diffusion coefficients deduced from QENS and NMR spin echo experiments [63]. A recent prelimin-voured statistically.…”