TROPOLONE MONOMER - VIBRATIONAL-SPECTRUM AND PROTON TUNNELING

Infrared matrix-isolation spectra are reported for the tropolone monomers C7H5O2H and C7H5O2D. Tropolone possesses an intramolecular hydrogen bond and the possibility for proton tunneling from one oxygen atom to the other. Clearcut multiplets attributed to tunneling are observed for the OD stretching mode and for heavy atom modes of both C7H5O2D and C7H5O2H. The (mixed) carbonyl stretching mode particularly seems to facilitate tunneling from one conformation to the other. The tunneling phenomena suggests that tropolone monomer has nearly C2v symmetry. As a crude estimate, the tunneling potential energy barrier is calculated to be less than 5600 cm-1 in the ground electronic state of C7H5O2D. The barrier is lower in the Π* electronic state than in the ground electronic state. A vibrational assignment that encompasses most of the 39 fundamental modes is proposed. The vibrations are classified using C2v symmetry species and a parallel vibrational analysis is presented for tropone, C7H6O, which is a true C2v molecule. © 1979.