Ultrafast Dynamics of a Molecular Switch from Resonance Raman Spectroscopy: Comparing Visible and UV Excitation
Ultrafast Dynamics of a Molecular Switch from Resonance Raman Spectroscopy: Comparing Visible and UV Excitation
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共振拉曼光谱的分子开关超快动力学：比较可见光和紫外激发
DOI：
10.1021/acs.jpca.2c05435
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Elles, Christopher G.
中科院分区：
文献类型：
--
作者：
Burns, Kristen H.;Elles, Christopher G.
共振拉曼光谱探测了二乙基乙烯（DAE）分子开关在激发进入前两个光学吸收带后的超快动力学。在可见光（750 - 560nm）和近紫外（420 - 390nm）波长处的拉曼激发与785 nm处的计算和实验非共振拉曼光谱相比，模式特异性共振增强揭示了两种电子激发态的不同frank - condon主动振动。可见波长下的共振增强与促进环还原反应的第一激发态的初始运动一致，而近紫外波长下的激发增强则突出了共轭主链和苯环拉伸模式与反应坐标正交的运动。结果支持一种机制，涉及从高能级的快速内部转换，然后在第一激发态上进行循环逆转。这些观测结果为DAE衍生物在可见光和近紫外激发后的反应性提供了新的信息。
Resonance Raman spectroscopy probes the ultrafast dynamics of a diarylethene (DAE) molecular switch following excitation into the first two optical absorption bands. Mode-specific resonance enhancements for Raman excitation at visible (750–560 nm) and near-UV (420–390 nm) wavelengths compared with the calculated and experimental off-resonance Raman spectrum at 785 nm reveal different Franck–Condon active vibrations for the two electronically excited states. The resonance enhancements at visible wavelengths are consistent with initial motion on the first excited-state that promotes the cycloreversion reaction, whereas the enhancements for excitation at near-UV wavelengths highlight motions involving conjugated backbone and phenyl ring stretching modes that are orthogonal to the reaction coordinate. The results support a mechanism involving rapid internal conversion from the higher-lying state followed by cycloreversion on the first excited state. These observations provide new information about the reactivity of DAE derivatives following excitation in the visible and near-UV.