Preferential Solvation of Some Divalent Transition Metal Ions in Water-Methanol Mixtures as Reviewed by the Measurements of 13C-NMR Paramagnetic Relaxation Rate

Eiji KUBOTA* and Nobuya TSUCHIYA

Department of Chemistry, Faculty of Science, Shinshu University;
Asahi, Matsumoto-shi 390-8621 Japan

A 13C-NMR spin-lattice relaxation time of methanol was measured with solutions of o-, m-BDS(BDS: benzenedisulfonate) and perchlorate of some divalent transition metals in water-methanol mixture. The comparison in NMR data between water-methanol mixture and pure methanol solution gave the number of methanol molecules that locate in the first solvation sphere of divalent transition metal ions. The results show that divalent transition metal ions are preferentially hydrated in all the Mn2+ and Cu2+ salt/H2O/MeOH systems, while in the Coo-BDS and Nio-BDS/H2O/MeOH systems, both Co2+ and Ni2+ show no preferential solvation behaviors, presumably due to the o-BDS2− counter ion effect.

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