EXCITED-STATE INTRAMOLECULAR PROTON-TRANSFER IN ANTHRALIN - QUANTUM-CHEMICAL CALCULATIONS AND FLUORESCENCE-SPECTRA

Quantum chemical calculations performed on anthralin (1,8-dihydroxy-9( 10H)-anthracenone) predict the possibility of an excited-state intramo lecular proton transfer process. Fluorescence excitation and emission spectra of the compound dissolved in n-hexane at ambient temperature r esults 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 quant um yield, The results are interpreted as an indication of a large equi librium geometry change upon excitation, associated with an excited-st ate intramolecular proton transfer process. (C) 1998 Elsevier Science B.V. All rights reserved.