On the ground and excited state molecular electronic structures and properties of benzanilide and its tautomer and their solvent dielectric modulations

Abstract

The electronic and structural properties of benzanilide have been computed 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 representation. The ground state geometries have been optimized with the AM1 method. The predicted normal S₁→ S₀ fluorescence of the amide form of the molecule, as observed experimentally also, has a mixed nπ^∗ +ππ^∗ character. The imidol tautomer is also predicted to have similar S₁'→ S₀' fluorescence. The predicted magnitudes of ΔE_S1' - _S0' of the imidol form and ΔE_{S1- S0} of the amide form compare well with the experimental results. The theoretically predicted ΔE_S0'-_S0 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 orders and the energies for different conformations have also been reported for both the tautomers in the ground as well as excited states, shedding some light on their important structural features and their solvent modulations.