Solvation Structure of Lithium Bromide in Concentrated Acetone Solutions

Abstract

Abstract Polarized Raman scattering and neutron diffraction measurements have been carried out for concentrated LiBr acetone solutions, in order to deduce detailed information on the solvation structure of Li+ in non-aqueous solutions. Isotropic Raman spectra observed for (LiBr)x[(CH3)2C=O]1−x with x = 0.02–0.06 exhibited a polarized peak at ν ≈ 370 cm−1 which is attributable to the interionic vibration of Li+···Br− ion pair which is formed in the solutions. The neutron distribution function around Li+, GLi(r), derived from the first-order difference function between 6Li/7Li isotopically substituted 6 mol% LiBr acetone-d6 solutions indicated the presence of a well-defined first solvation shell around Li+ in the solution. The nearest neighbor Li+···O(acetone) distance, rLiO, and coordination number, nLiO, were respectively determined to be 2.24(1) Å and 3.2(1), from the least squares fitting analysis for the observed difference interference function, ΔLi(Q). Structure parameters for the nearest neighbor Li+···Br− interaction were determined to be rLiBr = 2.86(2) Å and nLiBr = 0.8(1), respectively.