The electronic spectra of diphenyl and its sterically hindered derivatives

The electronic energy levels of diphenyl have been calculated by a Pariser, Parr and Pople method for angles between the two benzene rings of 0°, 45° and 90°. All singly but no doubly excited states have been considered. The results are compared with the electronic spectra of diphenyl and its sterically hindered derivatives and with the circular dichroism spectra of optically active diphenyl derivatives. Satisfactory agreement with experiment is found except for the calculated and measured rotational strengths. The results of the present work are compared with those of the ‘molecules in molecules’ method.