偶氮苯衍生物(E)-1-phenyl-2-((triisopropylsilyl)ethynyl)diazene的超快光异构动力学研究

Investigation of Ultrafast Photoisomerization Dynamics of Azobenzene Derivative(E)-1-Phenyl-2-((trisopropylsilyl)ethynyl)diazene

当暴露在特定波长的光下时,偶氮苯及其衍生物会通过异构化从反式转变为顺式.由于偶氮苯在光照下发生颜色变化的能力,它在各种分子器件和功能材料中得到了广泛应用.然而,尽管有大量关注实际应用方面的研究,但对偶氮苯光化学反应和顺反异构化背后的物理机制仍需进一步探索、本文采用飞秒受激拉曼光谱技术和瞬态吸收光谱技术结合量子化学计算方法,对偶氮苯衍生物trans-AZOTIPS((E)-1-phenyl-2-((triisopropylsilyl)ethynyl)diazene)超快异构化动力学过程进行了深入研究.结果显示,在光激发条件下,trans-AZOTIPS分子经历由激发态S_(1)向热基态S_(0)^(*)的快速跃迁,并伴随着沿C-N=N键进行的顺反异构化.此外,还考察了溶剂粘度对trans-AZOTIPS分子异构化过程的影响,并发现溶剂粘度变化不会影响其异构化的弛豫时间;这表明该异构化过程呈现出一-种被称为“呼啦扭转”的体积守恒的结构变化特征.最后,处于热基态S_(0)^(*)上的trans-AZOTIPS分子通过振动冷却过程回到基态S_(0).

When exposed to light at a specific wavelength,azobenzene and its derivatives experience a transformation from trans form to cis form through isomerization.Due to its ability to change color upon illumination,azobenzene finds extensive use in various molecular devices and functional materials.However,despite significant researches focused on practical applications,there are still ongoing investigations into the underlying mechanisms governing azobenzene’s photochemical reactions and isomerization.In this study,we employ femtosecond stimulated Raman spectroscopy(FSRS),and transient absorption spectroscopy,in conjunction with quantum chemical calculations,to elucidate the ultrafast isomerization dynamics of an azobenzene derivative known as trans-AZOTIPS((E)-1-phenyl-2-((triisopropylsilyl)ethynyl)diazene).The results demonstrate that upon photoexcitation,rapid isomerization occurs along the C−N=N bonds via the singlet excited state S_(1)to hot ground state(S_(0)^(*))state transition.Additionally,we explore the impact of solvent viscosity on the isomerization process and find that the duration of isomerization remains unaffected by variations in solvent viscosity.These results suggest that the isomerization pathway involves a volume-conserving motion known as“hula twist”.After that,the vibrational cooling process is obtained in S_(0)state.