New thermochemical parameter for describing solvent effects on IR stretching vibration frequencies. Communication 2. Assessment of cooperativity effects

Solvent effects on O-H stretching vibration frequency of methanol in hydrogen bond complexes with different bases, CH3OH···B, have been investigated by FTIR spectroscopy. Using chloroform as a solvent results in strengthening of CH3OH···B hydrogen bonding due to cooperativity between CH3OH···B and Cl3CH···CH3OH bonds. A method is proposed for quantifying the hydrogen bond cooperativity effect. The determined cooperativity factors take into account all specific interactions of the solute in proton-donor solvents. In addition, a method of estimation of cooperativity factors Ab and AOX in system (CH3OH)2···B is proposed. It is demonstrated that in such systems, the cooperativity factor of the OH···B bond decreases and that of the OH···O bond increases with increasing the acceptor strength of the base B. The obtained results are in a good agreement with the data obtained previously from matrix-isolation FTIR spectroscopy. © 2005 Elsevier B.V. All rights reserved