Solvation of anions in acetonitrile solutions: FTIR and quantum chemical study for Br, ClO, AsF, and CFSO.

Anion solvation in acetonitrile solutions was comparatively studied using FTIR spectroscopy and quantum chemical calculations at the RTF + MP2/6-311G** level of theory with solvation model density (SMD) corrections. Infrared spectra for all stable anionic complexes X(CHCN) (where X = Br (monatomic halide), ClO (polyatomic tetrahedral), AsF (polyatomic octahedral), CFSO (polyatomic ethane-like) and n = 1-8) were calculated and subsequently used in the analysis of the FTIR spectra of (BuN)X and LiX acetonitrile solutions across a wide range of concentrations. Spectroscopic manifestations of solvation were established for all X examined. The results for all four anions under investigation were generalized to reveal the regularities of anion solvation by acetonitrile.