FEMTOSECOND SPECTROSCOPIC STUDY ON SOME PHOTOCHROMIC AND ELECTROCHROMIC REACTIONS AND THEIR RESPONSE AT THE INTERFACE

用飞秒激光光谱、半经验分子轨道计算和电化学方法研究了一些二芳基乙烯衍生物、水杨醛基苯胺(SA)衍生物以及偶氮苯衍生物的Rh-和Ru-配合物的光致变色和电致变色反应。用原子力显微镜和时间分辨荧光SNOM研究了螺环吡喃衍生物在固体界面上的光致变色反应，发现SA发生了质子转移，时间常数为200~300fs，随后发生了结构变化。反应速率的溶剂依赖性很小，表明固相中发生了有效的光致变色反应。在二芳基乙烯衍生物中，根据Woodward-Hoffmann规则，首次证实了在没有任何中间体的情况下发生了闭环反应。该反应的活化能也可以忽略不计。此外，激发态si…的较大结构变化。在偶氮苯类化合物中，时间常数为1~10ps的S1态通过反转机制发生了反转异构化反应，时间常数为1~10ps，甚至在激发过程中也发生到S2态。Rh-偶氮苯的氧化还原行为不可逆地表现为反顺异构化，而Ru的氧化还原行为可逆地表现出从偶氮苯到MLCT态的超快激发能转移，但其氧化还原行为是可逆的。螺吡喃生成花菁的过程几乎不发生分子在固体界面上的置换。然而，J-聚集体是通过分子在热能作用下向μm移动100 nm而形成的，这些结果被认为是开发新的光致变色和电致变色材料以及纳米光电响应器件所必需的。较少

Photochromic and electrochromic reactions of some diarylethene derivatives, salicylidene aniline (SA) derivatives, and Rh- and Ru-complexes conjugated with azobenzene derivatives have been investigated by femtosecond laser spectroscopy, semi-empirical molecular orbital calculation, and electrochemical methods. Photochromic reaction of a spiropyran derivative on the solid interface has been also examined by AFM and time-resolved fluorescence SNOM.It was found that the proton transfer of SA took place with a time constant of 200 〜 300 fs followed by the structural change. The solvent dependence of the rate was negligibly small at R.T.indicating the efficient photochromic reaction in the solid phase. In diarylethene derivatives, the ring closure reaction was firstly confirmed to take place without any intermediates according to the Woodward-Hoffmann rule. The activation energy of the reaction was also found to be negligibly small. In addition, the large structural change in the excited si … More nglet state reduces the quantum yield of the photochromic reaction.In azobenzene derivatives, the trans-cis isomerization was found to occur from S1 state with a time constant of 1 〜 10 ps depending on the solvent viscosity through the inversion mechanism even in the excitation to the S2 state. Rh-complexes with azobenzene show trans-cis isomerization although their redox behaviors are irreversible, whereas Ru-complexes show ultrafast excitation energy transfer from azobenzene to MLCT state without any isomerization although their redox behaviors are reversible.Photochromic response at the solid interface was examined by scanning probe microscopy. The formation of merocyanine from spiropyran was confirmed to be almost no displacement of the molecules on the solid interface. However, the J-aggregate was formed through the large displacement of a few 100 nm to μm of molecules actrivated by the thermal energy.These results are considered to be indispensable to develop new photochromic and electrochromic materials and nanosized photo- and electro-responsive devices. Less