ON THE GROUND AND EXCITED-STATE MOLECULAR ELECTRONIC-STRUCTURES AND PROPERTIES OF BENZANILIDE AND ITS TAUTOMER AND THEIR SOLVENT DIELECTRICMODULATIONS

The electronic and structural properties of benzanilide have been comp uted in the gas phase as well as in various solvents with the help of the CNDO/S-CI reaction-field (RF) method in the image-charge represent ation. The ground state geometries have been optimized with the AM1 me thod. The predicted normal S-1-->S-0 fluorescence of the amide form of the molecule, as observed experimentally also, has a mixed n pi+pi p i character. The imidol tautomer is also predicted to have similar S- 1'-->S-0' fluorescence. The predicted magnitudes of Delta E(S1'-S0') o f the imidol form and Delta E(S1-S0) of the amide form compare well wi th the experimental results. The theoretically predicted Delta E(S0'-S 0), value also concurs with the experimental observation. The singlet- triplet splittings of both the tautomers of benzanilide are also well reproduced. The computed dipole moments, the C-N and the C-O bond orde rs and the energies for different conformations have also been reporte d for both the tautomers in the ground as well as excited states, shed ding some light on their important structural features and their solve nt modulations.