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

The complete active space (CAS) SCF method and multiconfigurational second-order perturbation theory (CASPT2) have been used to study the electronic spectra of indole, indene, benzimidazole, and 7-azaindole. Singlet and triplet excited states and transition properties in the absorption spectra, such as oscillator strengths and transition moment directions, have been computed and the experimental data interpreted in order to gain insight into the rich spectroscopy of these compounds, which are alternative candidates to indole as biochemical probes in the characterization of protein properties.