Metal ions in hydrogen bonded solvents: a gas phase perspective

Abstract

Recent experiments and complementary ab initio calculations have focused attention on studying multiply-charged metal–solvent [M·S_n]^q+ complexes in the gas phase. Although the preparation and study of such complexes presents a considerable experimental challenge, techniques capable of yielding quantitative signals are beginning to emerge. When the solvent (S) consists of a molecule capable of forming hydrogen bonds, e.g. H₂O or CH₃OH, evidence is frequently found of an extended solvent structure, which theory attributes to the formation of charge-enhanced hydrogen bonds. In some instances, these hydrogen bonds are formed in preference to completing the shell of solvent molecules, which should surround the central ion. As a consequence, gas phase and condensed phase experiments would appear to yield different solvation numbers; however, it is possible to rationalize the two data sets. Experiments on individual [M·S_n]^q+ complexes could lead to a molecular picture of the mechanism for hydrolysis; a process which could be viewed as the chemical consequences of hydrogen bonding.