Solvent conformation and ion solvation: From molecular to ionic liquids*
Shin-ichi Ishiguro, Yasuhiro Umebayashi, Kenta Fujii, and Ryo Kanzaki
Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
Abstract: Metal ions are solvated in solution, and, in a sterically congested organic solvent, those solvent molecules that are simultaneously bound to the metal ion will be subject to consequential steric interactions through space. The molecular structure of a solvent, particularly that of any functional groups in the vicinity of the coordinating atom to the metal ion, plays a key role in the solvation steric effect. Weak solvation steric effects lead to a distorted octahedral structure for six-coordinate transition-metal(II) ions, whereas strong steric effects lead to a decreased solvation number. In particular cases, the conformation of a solvent may undergo a change in response to coordination to the metal ion. Solvation steric effects play a decisive role in reaction thermodynamics and kinetics of the metal ion. Here, we show our recent results on solvation steric effects in terms of structure and thermodynamics, particularly, the conformational change of solvent and its effect on the metal-ion complexation.
Keywords: solution chemistry; solvent conformation; solvation structure; conformational change; molecular liquids; ionic liquids.
*Paper based on a presentation at the 29th International Conference on Solution Chemistry, Portorož, Slovenia, 20-25 August 2005. Other presentations are published in this issue, pp. 1559-1617.