Ion Solvation in Solution, Studied by Nuclear Magnetic Resonance Spectroscopy

The use of nuclear magnetic resonance spectroscopy for the study of the properties and structure of solvation shell complexes is discussed through the example of Co 2+ ions in methanol. New proton relaxation and shift measurements in solutions of Mn(ClO 4 ) 2 and Cr(ClO 4 ) 3 in anhydrous methanol are described and analyzed. The results yield kinetic and magnetic parameters for the [Mn(CH 3 OH) 6 ] 2+ and [Cr(CH 3 OH) 6 ] 3+ solvates. The dominant kinetic process for Mn 2+ involves exchange of whole molecules in and out of the solvation shell, while for Cr 3+ only the protolysis reaction of the hydroxyl protons affects the NMR resonance. Both ions have relatively long electron spin relaxation times and it is therefore not possible to observe their solvation shell directly. Preliminary results on Cu 2+ solvates are also discussed.