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

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 $T_{\text{1e}}{\mathrm{\hspace{0.17em}=\hspace{0.17em}T}}_{\text{2e}}$ . 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 ${\text{A\hspace{0.17em}/\hspace{0.17em}h\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}(1.74\hspace{0.17em}±\hspace{0.17em}0.03)\hspace{0.17em}×\hspace{0.17em}10}}^7\mathrm{Hz}$ and ${\tau }_e{\text{\hspace{0.17em}=\hspace{0.17em}1.7\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−12}}\sec$ at −10°C assuming $T_{\text{1e}}{\mathrm{\hspace{0.17em}=\hspace{0.17em}T}}_{\text{2e}}$ .