Interpretation of electronic spectra by configuration analysis: Absorption spectra of azanaphthalenes

Abstract

A theoretical investigation has been made on the electronic absorption spectra of four azanaphthalenes, quinoline, isoquinoline, quinoxaline, and phthalazine. The results of molecular orbital calculations performed by the Pariser-Parr-Pople method were subjected to the configuration analysis. The effects of aza-replacement are explained in relation to the position of replacement and to the molecular symmetry, and assignments of individual absorption bands are established. The intensification of the L b band caused by the aza-replacement is interpreted as due to the mixing of the L b state either with the L a or with the B b . It is shown that, in place of the B b band in naphthalene, α-aza compounds give two strong absorption bands which arise from a mixing of the B b ( B 1 u +) and A g − states of naphthalene.