CORRELATION BETWEEN DIPOLE MOMENT CHANGE AND EXTENT OF VIBRONIC INTENSITY BORROWING IN BENZENE DERIVATIVES

Author Institution: Department of Chemistry, University of Illinois UrbanaStudies of the near-ultraviolet spectra of several monosubstituted benzene derivatives have revealed a correlation between the size of the dipole moment change on excitation and the predominance of allowed over forbidden character in the transition. Molecules studied range from aniline, with dipole moment change of 0.91 Debye and no forbidden character, to phenyl isocyanide, with dipole moment change of 0.12 Debye and only 25\% allowed character. These findings may be explained in terms of the relative amount of charge trnasfer in the excited-state have functions and the influence of charge transfer on vibronic borrowing (Herzberg-Teller effect)