Quantum chemical simulation and low-temperature FTIR investigations of the structure and spectral characteristics of methanol monomer and dimer in an argon matrix

Abstract

Low-temperature FTIR spectra of methanol in an argon matrix are analyzed on the basis of B3LYP/cc- pVTZ and B3LYP/acc-pVQZ calculations of the geometry and IR spectra of methanol monomer and dimer. The adequacy of the scaled force fields is checked by the comparison of the calculated and experimental spectra of methanol isotopomers. Assignment of the absorption bands in the FTIR spectrum of methanol registered at 10 K to the monomer and dimer vibrations was made taking into account the torsion-vibration interaction. A series of the absorption bands caused by the formation of the intermediate cluster structures during the sample heating from 20 to 35 K was detected. Using the results of computer simulation of the methanol dimer interaction with Ar atoms, new possible mechanism of the broad absorption bands formation in the region of torsional, bending and stretching vibrations of a hydroxyl group of the dimer donor molecule appearing at the sample heating above 30 K was suggested.