Cooperativity effects in cyclic trifluoromethanol trimer: an ab initio study

For the first time, ab initio molecular orbital calculations are used to provide information on the dimer and cyclic trimer of trifluoromethanol. In order to better understand the system, the monomer is also investigated. Molecular geometries, binding energies, and harmonic vibrational frequencies of monomer, dimer and trimer are investigated at the Hartree-Fock Self-Consistent level using the 6-31+G(d,p), 6-31++G(2d,2p), and the 6-311++G(2d,2p) basis sets. Because the primary goal of this study is to examine cooperativity effects, particular attention is given to parameters such as O-O distances, electronic charge densities at the bond critical points, shifts in the stretching frequencies of the donor O-H bond, and the length of the donor O-H bond. The cooperativity factor found using the HF/6-311++G(2d,2p) method ranged from 1.49 to 1.90 for the three hydrogen bonds in the cyclic trimer. (C) 1998 Elsevier Science B.V.