Fluorescence excitation and emission spectra of 1,8-dihydroxyanthraquinone-d0 and – d 2in n-octane at 10 K

The fluorescence excitation and emission spectra in n-octane of 1,8-dihydroxyanthraquinone-d0 and -d2 at 10 K have been measured. Dual excitation and emission were observed as a consequence of excited state intramolecular proton transfer. A model, based on the Lippincott-Schroeder potential function, is proposed to predict the observed energy gaps and relative intensities of the transition. The isotopic effects are also explained. The Shpolskii matrices in n-octane show only one main site allowing a detailed vibrational analysis of the ground and the excited states. This furnished further evidence for the existence of excited state tautomers. The occurrence of an extra fluorescence was explained in terms of the ν(OH) stretching mode of the high frequency transition enhanced via vibronic coupling between the two ground states.