Specific effects of water on the relation processes of excited organic molecules

采用激光光解法、时间分辨热透镜法和荧光法研究了溶剂水对受激有机分子弛豫过程的影响。对于苯胺及其衍生物，光离是最主要的弛豫通道之一，而光离产生的阳离子自由基的极化稳定性是决定光离产率的重要因素。研究了1-羟基-2-乙酰萘酚（1H2AN）及其相关化合物激发态质子转移（ESIPT）反应，揭示了1-萘酚衍生物激发态的氢键相互作用。研究表明，1H2AN发生典型的ESIPT反应，而甲基-1-羟基-2-萘酸的激发态失活则没有发生ESIPT反应。阐明了这些化合物的电子结构对ESIPT反应的影响。此外，我们还发现1H2AN的ESIPT之后会发生更多的顺反异构化，从而产生激发的反式酮。用激光光解法研究了2,4-二甲氧基-6-（对聚氧氧基）-s-三嗪的光- fries重排中间体中3-异位氢的位移。动力学测量表明，水和质子溶剂通过相互氢交换反应加速了1,3-异位氢转移的速率。研究了水溶液中1,4-二甲氧基苯（DMB）三态与水合氢离子的电子转移（ET）反应，揭示了水合氢离子对水溶液中有机分子光松弛过程的影响。ET反应的发生是由DMB阳离子自由基的形成与三态DMB的消失相一致证实的。通过动力学分析，确定了ET反应的速率常数为7.5 × 10^6M^<-1>s-1。计算的ET反应的自由能变化（DELTAG^0 = +28kJmol^<-1>）与三态DMB到水合氢离子的ET反应速率一致。少

Effects of solvent water on the relaxation processes of excited organic molecules were studied by means of laser photolysis method, time-resolved thermal lensing method and fluorometry. For aniline and its derivatives, it was found that photoionization is one of the most dominant relaxation channel and that the polarization stabilization of the cation radical produced by photoionization is an important factor to determine the photoionization yield. Excited-state intramolecular proton transfer (ESIPT) reactions of 1-hydroxy-2- acetonaphthone (1H2AN) and related compounds were studied to reveal hydrogen-bonding interations in the excited state of 1-naphthole derivatives. The study showed that 1H2AN undergoes a typical ESIPT reaction, while the excited singlet state of methyl-1-hydroxy-2-naphthoate deactivates without ESIPT reactions. The effects of electronic structures on the ESIPT reaction were clarified for these compounds. Furthermore, it was found that ESIPT of 1H2AN is followed by … More cis-trans isomerization to produce an excited trans-keto form. The , 3-sigmatropic hydrogen shift in the photo-Fries rearranged intermediate of 2,4-dimethoxy-6-(p-tolyloxy)-s- triazine was investigated by using laser photolysis method. Kinetic measurements showed that water and also protic solvents accerelates the rate of the 1,3-sigmatropic hydrogen shift by mutual hydrogen exchange reactions. The electron transfer (ET) reaction from the triplet state of 1,4-dimethoxybenzene (DMB) to the hydronium ion in aqueous solution was studied to reveal effects of the hydronium ion on the photorelaxation processes of organic molecules in aqueous solution. The occurrence of the ET reaction was substantiated by formation of a DMB cation radical coinciding with disappearance of triplet DMB.From kinetic analyses, the rate constant for the ET reaction was determined to be 7.5 x 10^6M^<-1>s-1. The free energy change (DELTAG^0 = +28kJmol^<-1>) calculated for the ET reaction was consistent with the observed rate for the ET reaction from triplet DMB to the hydronium ion. Less