Golovina Galina V, Egorov Anton E, Khodot Evgenii N, Kostyukov Alexey A, Timokhina Elena N, Astakhova Tatiana Yu, Nekipelova Tatiana D
Emanuel Institute of Biochemical Physics RAS, Kosygin Str. 4, Moscow, 119334, Russia.
Zelinsky Institute of Organic Chemistry RAS, Leninskii Pr. 47, Moscow, 119991, Russia.
Photochem Photobiol Sci. 2024 Jan;23(1):177-187. doi: 10.1007/s43630-023-00511-4. Epub 2023 Dec 9.
Kinetic and thermodynamic parameters have been investigated for the thermal Z‒E isomerization of dihydroquinolylazotetrazole dyes with alkyl substituents (Me, t-Bu, and Adm) at positions 1 (dyes 2) and 2 (dyes 3) of the tetrazole moiety in two solvents of different polarity, acetonitrile (MeCN) and toluene. The experimental results show crucial dependence of these parameters on a substituent position in the tetrazole moiety and on a solvent. For dyes 2, E and ΔH are lower in MeCN than in toluene that results in a high increase in the lifetimes of the Z isomers: from milliseconds in MeCN to minutes in toluene. For dyes 3, the difference in E and ΔH in the two solvents is opposite: E and ΔH are by more than 20 kJ mol higher in MeCN, nevertheless, the rate constants for 3 in toluene are comparable with those in MeCN at the ambient temperature and the difference in the behavior is determined by the value of negative entropy of activation. Quantum-chemical calculations of the thermal Z‒E isomerization show the possibility of the process to occur via crossing from the S to the thermally induced T state. The contribution of this path is highest for 3 in toluene. The analysis of the absorption spectra demonstrates that for the E isomers, the n‒π* and π‒π* transitions are within the long-wavelength absorption band and their positions relative each other are opposite in the solvents: the n‒π* transition is blue-shifted relative to the π‒π* transition in MeCN and is red-shifted in toluene.
研究了二氢喹啉基偶氮四唑染料在四唑部分的1位（染料2）和2位（染料3）带有烷基取代基（甲基、叔丁基和金刚烷基）时，在两种不同极性的溶剂乙腈（MeCN）和甲苯中发生的热Z-E异构化反应的动力学和热力学参数。实验结果表明，这些参数强烈依赖于四唑部分的取代基位置和溶剂。对于染料2，在乙腈中的E和ΔH低于甲苯中的，这导致Z异构体的寿命大幅增加：从乙腈中的毫秒级增加到甲苯中的分钟级。对于染料3，两种溶剂中E和ΔH的差异相反：在乙腈中E和ΔH高出20 kJ/mol以上，然而，在室温下，染料3在甲苯中的速率常数与在乙腈中的相当，行为差异由活化熵的负值决定。热Z-E异构化反应的量子化学计算表明，该过程有可能通过从S态跃迁到热诱导的T态发生。对于染料3在甲苯中的情况，这条路径的贡献最大。吸收光谱分析表明，对于E异构体，n-π和π-π跃迁在长波长吸收带内，它们在溶剂中的相对位置相反：在乙腈中，n-π跃迁相对于π-π跃迁发生蓝移，在甲苯中发生红移。
