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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Excited-State Intramolecular Hydrogen Transfer (ESIHT) of 1,8-Dihydroxy-9,10-anthraquinone (DHAQ) Characterized by Ultrafast Electronic and Vibrational Spectroscopy and Computational Modeling
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Excited-State Intramolecular Hydrogen Transfer (ESIHT) of 1,8-Dihydroxy-9,10-anthraquinone (DHAQ) Characterized by Ultrafast Electronic and Vibrational Spectroscopy and Computational Modeling

机译：1,8-二羟基-9,10-蒽醌（DHAQ）的激发态分子内氢转移（ESIHT）的超快电子和振动光谱和计算模型表征

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摘要

We combine ultrafast electronic and vibrational spectroscopy and computational modeling to investigate the photoinduced excited-state intramolecular hydrogen-transfer dynamics in 1,8-dihydroxy-9,10-anthraquinone (DHAQ) in tetrachloroethene, acetonitrile, dimethyl sulfoxide, and methanol. We analyze the electronic excited states of DHAQ with various possible hydrogen-bonding schemes and provide a general description of the electronic excited-state dynamics based on a systematic analysis of femtosecond UV/vis and UV/IR pump-probe spectroscopic data. Upon photoabsorption at 400 nm, the S_2 electronic excited state is initially populated, followed by a rapid equilibration within 150 fs through population transfer to the S_1 state where DHAQ exhibits ESIHT dynamics. In this equilibration process, the excited-state population is distributed between the 9,10-quinone (S_2) and 1,10-quinone (S_1) states while undergoing vibrational energy redistribution, vibrational cooling, and solvation dynamics on the 0.1-50 ps time scale. Transient UV/vis pump-probe data in methanol also suggest additional relaxation dynamics on the subnanosecond time scale, which we tentatively ascribe to hydrogen bond dynamics of DHAQ with the protic solvent, affecting the equilibrium population dynamics within the S_2 and S_1 electronic excited states. Ultimately, the two excited singlet states decay with a solvent-dependent time constant ranging from 139 to 210 ps. The concomitant electronic ground-state recovery is, however, only partial because a large fraction of the population relaxes to the first triplet state. From the similarity of the time scales involved, we conjecture that the solvent plays a crucial role in breaking the intramolecular hydrogen bond of DHAQ during the S_2/S_1 relaxation to either the ground or triplet state.
机译：我们结合超快的电子和振动光谱和计算模型来研究在四氯乙烯，乙腈，二甲基亚砜和甲醇中的1,8-二羟基-9,10-蒽醌（DHAQ）中的光致激发态分子内氢转移动力学。我们用各种可能的氢键方案分析了DHAQ的电子激发态，并基于对飞秒UV / vis和UV / IR泵浦探针光谱数据的系统分析，提供了电子激发态动力学的一般描述。在400 nm处发生光吸收后，最初会填充S_2电子激发态，然后在150 fs内通过群体转移到S_1状态（其中DHAQ表现出ESIHT动力学）快速平衡。在此平衡过程中，激发态总体分布在9,10-醌（S_2）和1,10-醌（S_1）态之间，同时在0.1-50 ps上经历振动能的重新分布，振动冷却和溶剂化动力学。时间尺度。甲醇中的瞬态UV / vis泵浦探针数据还表明了亚纳秒级的附加弛豫动力学，我们将其归因于DHAQ与质子溶剂的氢键动力学，影响了S_2和S_1电子激发态的平衡种群动态。最终，两个激发的单重态以139至210 ps的溶剂依赖性时间常数衰减。但是，伴随的电子基态恢复只是部分的，因为很大一部分人口放松到了第一个三重态。从所涉及的时间尺度的相似性，我们推测溶剂在S_2 / S_1弛豫到基态或三重态期间，在破坏DHAQ的分子内氢键中起关键作用。

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