Hydrogen bonding and cooperative effects in mixed dimers and trimers of methanol and trifluoromethanol:: An ab initio study

Ab initio calculations are used to provide information on the mixed dimers and cyclic trimers of the methanol-trifluoromethanol system. In order to better understand the systems, the monomers and their corresponding dimers and trimers are also investigated. Molecular structures and harmonic frequencies are obtained at the B3LYP/6-31111G(d, p) level. Interaction energies are calculated with the MP2 and B3LYP methods using the 6-31111G( d, p), 6-31111G( 2d, 2p), and 6-311++G(3d, 2p) basis sets for the dimers and heterodimers. The 6-31111G( d, p) basis set was used to calculate the interaction energies for the trimers and heterotrimers. Because the primary goal of this study is to examine cooperative effects, particular attention is given to parameters such as O...O distances, electronic charge densities at the bond critical points, enhanced dipole moments, shifts in the stretching frequencies of the donor O-H bond, and the length of the donor O-H bond. (C) 1999 American Institute of Physics. [S0021-9606(99)30613-9].