Quantum chemical calculations performed on anthralin (1,8-dihydroxy-9(10H)-anthracenone) predict the possibility of an excited-state intramolecular proton transfer process. Fluorescence excitation and emission spectra of the compound dissolved in n-hexane at ambient temperature results in an unusually large fluorescence Stokes shift of 10500 cm−1. The emission appears as a broad band with a maximum at 17500 cm−1 and is characterized by a low and nearly temperature-independent quantum yield. The results are interpreted as an indication of a large equilibrium geometry change upon excitation, associated with an excited-state intramolecular proton transfer process.
Møller, S., Andersen, K. B., Spanget-Larsen, J., & Waluk, J. (1998). Excited state Intramolecular Proton Transfer in Anthralin: Quantum Chemical Calculations and Fluorescence Spectra. Chemical Physics Letters, 291(1-2), 51-56. https://doi.org/10.1016/S0009-2614(98)00546-6