Interpretation of electronic spectra by configuration analysis: Absorption spectra of monosubstituted naphthalenes

Abstract

The electronic absorption spectra of four monosubstituted naphthalenes, α-, β-naphthols, and α-, β-naphthylamines have been investigated by means of configuration analysis with particular attention to the dependence of spectra on the position of substitution and on the electron-donating power of the substituent. The results of molecular orbital calculations based on the Pariser-Parr-Pople method are analyzed in terms of locally excited states and intramolecular charge-transfer configurations. The characteristic changes in location and polarization of the L b , L a , and B b bands caused by substitution at the α- or β-position are adequately explained by the analysis. Two strong absorption bands of α-substituted naphthalenes, which appear in place of the B b band of naphthalene, are shown to result from a mixing of the B 3u +(B b) and A g − states. The amino group exerts a great influence on the electronic structure of the parent molecule, so that the B b band cannot be identified in the spectrum of β-naphthylamine.