The structure of the binary phenol-methanol cluster: A comparison of experiment and ab initio theory

The structure, energetics, vibrations and barrier to internal rotation of t he binary phenol-methanol cluster are calculated at different levels of the ory and compared to the results of a rotationally resolved S-1 <-- S-0 elec tronic spectrum. The structure of the phenol-methanol cluster is determined by a hydrogen bond and by a dispersive interaction of the methyl group wit h the aromatic ring. To account for the correct balance between these two a ttractive forces, computational methods have been employed which include el ectron correlation. The barrier to internal rotation of the methyl group ha s been determined from the experiment and compared to the lowest energy pat h at a relaxed ab initio energy surface. Furthermore, an ab initio normal m ode analysis is performed and compared to experimental intermolecular vibra tional frequencies for both electronic states. (C) 2001 Elsevier Science B. V. All rights reserved.