The relative sensitivities of oscillator strengths and transition energies in an electronic band system to solvent and substitutent perturbations have allowed the assignment of the electronic bands in pentachloroaniline, pentafluoroaniline, 4-chloroaniline and aniline. While the 'Lb, 'L, and 'I&, transitions are distinct in pentachloroaniline, the 'L, and '& transitions appear to be mixed in pentafluoroaniline, 4-chloroaniline or aniline. In all these compounds, except aniline, the 'Lb transition shows vibrational bands which are most distinct in nonpolar solvents. Analysis of the vibrational contours and Franck-Condon envelope showed changes in equilibrium nuclear configuration as the origin of the vibrational bands and that in pentachloroaniline and pentafluoroaniline different vibrational modes are responsible for intensity borrowing characteristic of the 'Lb transition.
Determination of excited state dipole moment relative to ground states by solvent shift of the transition energy of an electronic band reveals that the excited states of all transitions have more charged character, the charge transfer character of the 'L, transition being dominant.