STRUCTURE AND VIBRATIONS OF CATECHOL IN THE S-1 STATE AND IONIC GROUND-STATE

To determine structure and vibrations of catechol and d2-catechol (C6H 4(OD)(2)) in the ionic ground state, MATI spectra as well as ab initio and DFT calculations are presented. The comparison of the experimenta lly observed vibrational frequencies with the calculated values leads to a complete assignment of all vibrations. CASSCF and DFT calculation s predict a planar geometry of catechol in the S-0 and D-0 states. CAS SCF calculations for the S-1 state show that the free OH group of cate chol is rotated out of the plane of the aromatic ring by similar to 24 degrees. This calculation supports the assumptions of earlier experim ental work. The adiabatic excitation energies (S-1 <-- S-0) and the ad iabatic ionization potentials of catechol and its deuterated isotopome r can be predicted by CASSCF calculations including zero-point energie s and MP2 corrections. (C) 1998 Elsevier Science B.V. All rights reser ved.