FT-Raman spectroscopic study of ionic association and solvation in acrylonitrile solutions of calcium and magnesium perchlorate

Solutions of magnesium or calcium perchlorate in acrylonitrile (propenenitrile), in a range of concentrations [1-3 mol kg(-1) for Mg(ClO4)(2) and 1-6 mol kg(-1) for Ca(ClO4)(2)], have been analysed by FT-Raman spectroscopy. The new bands in the nu(CN) region arising from the bound species, M(2+)...(acrylonitrile)(n), have been examined in detail using deconvolution and band-fitting procedures. Solvation numbers of six (at infinite dilution) were calculated for both cations. The data obtained in the analysis of the perchlorate anion nu(1) (symmetric stretch) band show important differences in the association behaviour of the cations. Solutions of magnesium perchlorate indicate the presence of only one associated species. On the other hand, calcium perchlorate solutions show more complicated features and up to three different associated species could be identified. The stoichiometry and structures of these coordination species are discussed.