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Excited State Intramolecular Proton Transfer of 1-Hydroxyanthraquinone
Si-mei Sun, Song Zhang*, Kai Liu, Ya-ping Wang, Miao-miao Zhou, Bing Zhang
State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
Abstract:
The excited state intra-molecular proton transfer dynamics of 1-hydroxyanthraquinone in solution are investigated by femtosecond transient absorption spectroscopy and quantum chemistry calculations. Two characteristic bands of excited state absorption and stimu-lated emission are observed in transient absorption spectra with the excitation by the pump wavelength of 400 nm. From the delayed stimulated emission signal, the time scale of the intra-molecular proton transfer is determined to be about 32 fs. The quantum chemistry calculations show that the molecular orbits and the order of the S2 and S1 states are rever-sal and a conical intersection is demonstrated to exist along the proton transfer coordinate. After proton transfer, the second excited state of tautomer populated via the conical intersection undergoes the internal conversion with ~200 fs and the following intermolecular energy relaxation with ~16 ps. The longer component 300 ps can be explained in terms of the relaxation from excited-state tautomer to its ground state. From our observations, two proton transfer pathways via a conical intersection are proposed and the dominated one preserves the molecular orbits.
Key words:  Proton transfer, Conical intersection, Transient absorption spectroscopy, 1-Hydroxyanthraquinone
FundProject:
1-羟基蒽醌的分子内质子转移动力学
孙四梅, 张嵩*, 刘凯, 王雅萍, 周淼淼, 张冰*
中国科学院武汉物理与数学研究所,波谱与原子分子物理国家重点实验室,武汉 430071
摘要:
利用飞秒瞬态吸收光谱结合量化计算研究了1-羟基蒽醌在溶剂中的激发态分子内质子转移动力学. 分子受到400 nm光激发后的瞬态吸收谱呈现出激发态吸收和受激辐射两个光谱带. 受激辐射信号较激发态吸收信号滞后出现,由此确定质子转移时间是32 fs. 量化计算表明分子在沿质子转移路径衰变时,分子轨道和能级次序发生了反转,形成锥形交叉. 在质子转移之后,经锥形交叉布居的电子态发生内转换和分子间能量弛豫,时间分别是200 fs和16 ps. 基态回复时间是300 ps. 通过实验和理论研究,证实存在两个质子转移路径,其中主要的衰变路径保持了原来轨道的性质.
关键词:  质子转移,锥形交叉,飞秒瞬态吸收光谱,1-羟基蒽醌
DOI:10.1063/1674-0068/28/cjcp1504078
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