Geometrical Structures of Excited States of Conjugated Molecules: Benzene, Naphthalene, Azulene, and Heptalene
- 1 February 1972
- journal article
- Published by Oxford University Press (OUP) in Bulletin of the Chemical Society of Japan
- Vol. 45 (2) , 384-388
- https://doi.org/10.1246/bcsj.45.384
Abstract
A semiempirical SCF CI MO method used in combination with the variable bond-length technique, which has proved to be quite successful in predicting the ground-state geometrical structures of conjugated molecules, has been applied with modifications suitable to their excited states. The values of the parameters appearing in the expression of the resonance integral were adjusted so as to reproduce both the absorption and fluorescence spectra of benzene. The lower three singlet states (1B2u, 1B1u, and 1E1u) and the lowest triplet state (3B1u) of benzene, the lower two singlet states 1B1u and 1B2u) of naphthalene, the lower two singlet states (1B2 and 1A1) of azulene, and the lowest singlet state of heptalene are examined. It is predicted that the 1B1u and 3B1u states of benzene have the antiquinoidal and quinoidal conformations of the D2h symmetry respectively, and that the symmetry of the lowest singlet state of heptalene is higher than that (C2h) of the ground state.Keywords
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