Nuclear magnetic relaxation as a selective probe of solute-solvent and solute-solute interactions in multi-component mixtures

Abstract

Intermolecular nuclear magnetic relaxation may represent a powerful tool for the detection and study of weak, nonspecific molecular interactions in liquid solutions. Two intermolecular relaxation mechanisms, the electric quadrupole-field gradient interaction and the magnetic dipole-dipole relaxation are briefly described and recent applications are presented. The quadrupolar relaxation of 131Xe in water is shown, where the Xe atom can be regarded as an ideal hydrophobic model particle. Information about the dynamic behavior of water near the dissolved Xe is derived. 21Ne and 131Xe relaxation is used to probe electric field gradients acting in molecular liquids. By 81Br and 131Xe relaxation an attractive interaction between anions and Xe in aqueous solution is found. Finally, the application of intermolecular dipole-dipole interaction with respect to self-association of small hydrophobic particles in aqueous solutions is demonstrated. Salt effects on self-association are detected and their connection to the Hofmeister series is discussed.