Division of Frontier Materials Science and Center for Advanced Interdisciplinary Research, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Phys Chem Chem Phys. 2018 Aug 1;20(30):19776-19783. doi: 10.1039/c8cp01467a.
The one- and two-photon cycloreversion reactions of a fluorescent diarylethene derivative with oxidized benzothiophene moieties were investigated by means of ultrafast laser spectroscopy. Femtosecond transient absorption spectroscopy under the one-photon excitation condition revealed that the excited closed-ring isomer is simply deactivated into the initial ground state with a time constant of 2.6 ns without remarkable cycloreversion, the results of which are consistent with the very low cycloreversion reaction yield (<10-5) under steady-state light irradiation. On the other hand, an efficient cycloreversion reaction was observed under irradiation with a picosecond laser pulse at 532 nm. The excitation intensity dependence of the cycloreversion reaction indicates that a highly excited state attained by the stepwise two-photon absorption is responsible for the marked increase of the cycloreversion reaction, and the quantum yield at the highly excited state was estimated to be 0.018 from quantitative analysis, indicating that the reaction is enhanced by a factor of >1800.
通过超快激光光谱学研究了具有氧化苯并噻吩部分的荧光二芳基乙烯衍生物的单光子和双光子环回反旋反应。在单光子激发条件下的飞秒瞬态吸收光谱研究表明，激发的闭环异构体在没有明显环回反旋的情况下简单地以 2.6 ns 的时间常数失活到初始基态，这一结果与稳态光辐照下非常低的环回反旋反应产率（<10-5）一致。另一方面，在 532nm 的皮秒激光脉冲照射下观察到有效的环回反旋反应。环回反旋反应的激发强度依赖性表明，逐步双光子吸收达到的高激发态负责显著增加环回反旋反应，并且通过定量分析估计高激发态的量子产率为 0.018，表明反应增强了 >1800 倍。
