Sunghwan Kim - Fluorescence Excitation and Ultraviolet Absorption Spectra and Theoretical Calculations for Benzocyclobutane. Vibrations and Structure of its Excited S1(π,π*) Electronic State

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      Publication Details (including relevant citation   information):

      H.W. Shin, E.J. Ocola, S. Kim, and J. Laane;

      Journal of Chemical Physics, 2014, 140,   034305.



      The fluorescence excitation spectra of jet-cooled   benzocyclobutane have been recorded and together with its   ultraviolet absorption spectra have been used to assign the   vibrational frequencies for this molecule in its S1(π,π(*))   electronic excited state. Theoretical calculations at the   CASSCF(6,6)/aug-cc-pVTZ level of theory were carried out to   compute the structure of the molecule in its excited state. The   calculated structure was compared to that of the molecule in its   electronic ground state as well as to the structures of related   molecules in their S0 and S1(π,π(*)) electronic states. In each   case the decreased π bonding in the electronic excited states   results in longer carbon-carbon bonds in the benzene ring. The   skeletal vibrational frequencies in the electronic excited state   were readily assigned and these were compared to the ground state   and to the frequencies of five similar molecules. The vibrational   levels in both S0 and S1(π,π(*)) states were remarkably harmonic   in contrast to the other bicyclic molecules. The decreases in the   frequencies of the out-of-plane skeletal modes reflect the   increased floppiness of these bicyclic molecules in their   S1(π,π(*)) excited state.


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