Solvation of Co(II) in Methanol and Water Enriched in Oxygen-17

Abstract

The solvation sphere of cobaltous ion in oxygen-17-enriched methanol and water solutions was observed by oxygen-17 magnetic resonance. The chemical shift between the coordinated methanol molecules and the bulk methanol and the transverse relaxation times of oxygen-17 in the two environments were measured in the temperature range of −27.5° to +21°C. The hyperfine coupling constant between the cobaltous ion unpaired electrons and the oxygen-17 nuclei was found to be temperature independent and its value −(1.70 ± 0.03) × 107 Hz. The relaxation time of the unpaired electrons of the cobaltous ion was calculated and found to be 7 × 10−13 sec at 25°C, assuming T1e = T2e. The dipolar contribution to the relaxation rate of the oxygen-17 was calculated and found to be about 1% of the hyperfine contribution. The oxygen-17 chemical shift between the coordinate water molecules and the noncoordinated water molecules and their transverse relaxation times were measured at temperatures of −15°, −10°, and −5°C. The hyperfine coupling constant and the unpaired electron relaxation time were found to be A / h = − (1.74 ± 0.03) × 107Hz and τe = 1.7 × 10−12sec at −10°C assuming T1e = T2e.