1,3(n-π*) excited states of benzaldehyde

Abstract

Geometries of the first triplet and first singlet n-π* excited states of benzaldehyde have been optimized using the sindo 1 molecular orbital wave-function (with CI) and the Newton-Raphson method. The triplet excited state geometry of the molecule is found to be appreciably non-planar whereas that of the singlet excited state is planar. A crossing of molecular orbitals occurs in going from the ground state equilibrium geometry to the triplet and singlet n-π* excited state equilibrium geometries. Existence of the para-directing effect of the singlet n-π* transition for electronic charges found in an earlier work is confirmed by the present work. The triplet n-π* excitation rearranges electronic charges mainly on the CHO group. It is found that the dipole moment of the molecule would appreciably increase following the singlet n-π* excitation whereas the same would appreciably decrease following the triplet n-π* excitation. © 1985 Indian Academy of Sciences.