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

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 S-1 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 S-1 state to the tautomer S-1 state, and the VR process is observed in the time constant of 4.1 ps. Ultimately, the tautomer S-1 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. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The photoinduced dynamics of excited-state intramolecular proton transfer (ESIPT) and vibration relaxation (VR) of 1,8-DHAQ in ethanol were investigated using time-resolved transient absorption spectroscopy and quantum chemical calculations. The results showed dual fluorescence from the S-1 state, with ESIPT process occurring in 96.8 fs and VR process in 4.1 ps, leading to the decay of the tautomer S-1 state within 269.1 ps. This mechanism was summarized through a schematic diagram of four electronic states and vibrational energy levels.