Spectroscopic investigation of ternary solutions: H2OCH3CNCu(ClO4)2☆

Abstract Over a large range of concentrations in the ternary solutions H 2 OCH 3 CHCu(ClO 4 ) 2 , information about the various intermolecular interactions are extracted from the characteristic spectra of each component present: water (OH/D stretching vibration), CH 3 CN (CN stretching vibration), Cu 2+ (electronic transition on the visible region) and (ClO 4 ) − ion (ClO stretching vibration). The formation of contact ion pairs seems to become important only at salt concentrations above 0.05 mol l −1 . Using weighted IR difference spectra WDS it is possible to separate the spectrum of hydrate-water of the copper(II) ion from other H-bonded complexes present. The independent determination of the number of water and cyanomethane molecules interacting with the copper(II) ion is in agreement with a solvation number of 6. The composition of the solvation shell of the cation depends strongly on the composition of the solvent mixture. Qualitative agreement is found between these experimental results and theoretical considerations.