Calculation of Vibrational Spectra of Coordinated Perchlorate Ion in Dipolar Aprotic Solvents

Abstract

541.64:536The vibrational spectrum of perchlorate ion coordinated to Li + , Na + , and Mg 2+ cations in dipolar aprotic solvents (DAS) was studied using Hartree-Fock methods not taking into account (RHF) and accounting partially for electron correlation (MP2) and B3LYP density functional theory within the polarized continuum model (PCM). Experimental and calculated spectrum-structure correlations for coordinated perchlorate-ion complexes in DAS were analyzed. It was found that the best fi t of the experimental and calculated vibrational spectra was achieved by taking into account the electron correlation and non-specifi c solvation.Keywords: perchlorate ion, dipolar aprotic solvents, vibrational spectrum, RHF, B3LYP, and MP2 quantum-chemical methods, polarized continuum model, spectrum-structure correlations.Introduction. Modern methods for establishing the structures of ionic complexes in electrolyte solutions are based on comparisons of experimental and calculated vibrational spectra for the possible molecular motifs. Signifi cant discrepancies that hinder practical implementation of these methods arise even for the best non-empirical methods if the solvent is not taken into account. Differences in vibrational spectra of free anions and those coordinated to cations are widely used to study ion-ion interactions in electrolyte solutions in dipolar aprotic solvents (DAS). IR spectroscopic evidence of perchlorate coordination by Li + , Na + , and Mg 2+ in contact-ion pairs (CIP) in acetonitrile (AN) [1], pyridine (Py) [2], and acetone (Ac) [3] was obtained. Bands due to anion vibrations in CIP and ionic trios and quartets were observed in IR spectra of