STRUCTURE AND VIBRATIONS OF CATECHOL(METHANOL)(1) IN THE S-0 AND S-1 STATE

The structure as well as the inter- and intramolecular vibrations of t he catechol (methanol)(1) cluster are investigated both experimentally and theoretically. By using resonant two-photon ionization (R2PI) and dispersed fluorescence (DF) spectroscopy, the vibrational transitions of the S-0 and S-1 state are obtained. In order to find the correspon ding vibrations of the S-0 and S-1 state, DF spectra are recorded by p umping the electronic origin and the most intense vibrations of the R2 PI spectrum. According to ab initio calculations performed at the Hart ree-Fock level [6-31G(d,p) basis], including MP2, BSSE, and ZPE (zero point energy) corrections, the most stable structure turns out to be t ranslinear. The calculated vibrational frequencies are in close agreem ent to the experimental values. Since the catechol(methanol)(1) cluste r has no symmetry, all intermolecular fundamental vibrations of the S- 0 and S-1 state spectra can be assigned. A large number of combination bands and overtone vibrations are observed in the low frequency regio n (<200 cm(-1)) of the S-0 and S-1 state spectra. From the DF spectrum obtained by pumping the low frequency rho(1) vibration, it can be con cluded that the catechol(methanol), cluster undergoes a geometry chang e in the S-1 state. The OH ... O bond turns out to be nonplanar with r espect to the aromatic plane. This confirms the results reported for c atechol and the catechol(H2O)(1) cluster. (C) 1997 American Institute of Physics.