Infrared and electronic spectra of radicals produced from 2-naphthol and carbazole by UV-induced hydrogen-atom eliminations.

The photoreaction mechanisms of 2-naphthol and carbazole in low-temperature argon matrices have been investigated by infrared and electronic absorption spectroscopy with aids of density-functional-theory (DFT) and time-dependent DFT (TD-DFT) calculations. When the matrix samples were irradiated upon UV light, 2-naphthoxyl and N-carbazolyl radicals were produced by the elimination of the H atom in the O-H group of 2-naphthol and in the N-H group of carbazole, respectively. The observed IR and electronic absorption spectra of the radicals were reproduced satisfactorily by the quantum chemical calculations. To understand a role of the radicals in the excited-state proton transfer (ESPT), the fluorescence and excitation spectra of 2-naphthol and carbazole were measured in aqueous solution at room temperature as well as in the low-temperature argon matrices. It was found that the intensity of the fluorescence emitted from carbazole anion in aqueous solution decreased when oxygen gas was blown into the solution.