Ultrafast investigation of intramolecular proton transfer dynamics and vibration relaxation in 1,8-dihydroxyanthraquinone

Abstract

Photoinduced dynamics of excited-state intramolecular proton transfer (ESIPT) and vibration relaxation (VR) of 1,8-DHAQ in ethanol are investigated by time-resolved transient absorption spectroscopy combined with the quantum chemical calculations. Experimental and calculated results show dual fluorescence is obtained from the S1 state of the normal form of 9,10-quinone and the tautomer form of 1,10-quinone. Three characteristic bands of excited state absorption and stimulated emission are observed in transient absorption spectroscopy upon excitation with ultrafast laser pulses at 390 nm. ESIPT process happens within 96.8 fs from the normal S1 state to the tautomer S1 state, and the VR process is observed in the time constant of 4.1 ps. Ultimately, the tautomer S1 state decays within 269.1 ps for a deactivation pathway of emitting fluorescence. The mechanism of ESIPT dynamics and ultrafast excited-state dynamics in 1,8-DHAQ in ethanol is concluded by a schematic diagram of four electronic states and vibrational energy levels.