Direct Determination of the Relationship between the Intramolecular Oxygen-Hydrogen Bond Length and Its Stretching Vibrational Frequency of the Methanol Molecule in the Liquid State

Time-of-flight (TOF) neutron diffraction measurements on pure liquid deuterated methanol and concentrated methanolic LiClO4 and LiTFSA solutions have been carried out to investigate the effect of intermolecular hydrogen bonds on the intramolecular O-D distance (r(OD)) of the methanol molecule in the liquid state. Intramolecular parameters for the methanol molecule are determined by the least-squares fitting analysis of the neutron total interference term observed in the high-Q region. Attenuated total reflection (ATR) IR spectra have been measured for methanolic solutions of natural abundance to determine the gravitational center frequency (nu(OH)) of the stretching vibrational band of the methanol molecule. The relationship between r(OD) and nu(OH) is approximated well by a linear function. The value d nu(OH)/dr(OD) = -17000 +/- 3000 cm(-1) angstrom(-1) has been derived from the slope of the fitted function. It has been revealed that the O-D bond length of the methanol molecule is sensitively affected by the intermolecular hydrogen bonding interaction.