A theoretical study of the absorption spectra of indole and its analogs: indene, benzimidazole, and 7-azaindole

The complete active space (CAS) SCF method and multiconfigurational second- order perturbation theory (CASPT2) have been used to study the electronic s pectra of indole, indene, benzimidazole, and 7-azaindole. Singlet and tripl et excited states and transition properties in the absorption spectra, such as oscillator strengths and transition moment directions, have been comput ed and the experimental data interpreted in order to gain insight into the rich spectroscopy of these compounds, which are alternative candidates to i ndole as biochemical probes in the characterization of protein properties. (C) 2000 Elsevier Science B.V. All rights reserved.