Nuclear Magnetic Resonance Study of the Solvation of Ni++ in Methanol and Methanol—Water Mixtures

Abstract

Proton magnetic resonance spectra of solutions of Ni(ClO4)2 in acidified methanol and in methanol—water mixtures are reported. Separate peaks for the bulk methanol and for the methanol bonded to Ni++ are observed. From the temperature dependence of the peak frequencies a hyperfine interaction constant between the Ni++ and the methyl protons of the bonded methanol of +7.9×105 cps was obtained. At low temperatures, the linewidth is determined predominantly by electron—proton dipole—dipole interaction. The relevant correlation time is the electron relaxation time, which is about 3×10—12sec. This time decreases with increasing temperature, with an apparent activation energy of 1.3 kcal mole—1. At the higher temperatures methanol exchange contributes to the linewidth. The addition of water to the solvent increases the rate of exchange. This is ascribed to the formation of mixed water—methanol complexes.