Ab initio study on the photochemical reaction of diarylethenes and the molecular design of novel diarylethenes

π共轭分子具有广泛的光化学行为，在实验和理论上都引起了极大的兴趣。尽管人们对其光化学行为进行了大量的研究，但大部分的光化学行为还没有得到合理的解释。在本研究项目中，我们从理论上考察了二芳乙烯作为一种分子光存储器的光化学性质。我们还研究了另一种偶联azulene π体系的光化学性质。各研究主题的实际结果如下：1)二乙烯光环化的锥形交联（CIX）。CIX是了解二乙烯光化学最重要的成分。在CASSCF计算中，发现CIX不具有对称性，而反应物和生成物都具有C_2对称性。1) azulene的S_1-S_0内转化azulene是一种众所周知的违反Kasha规则的分子。50年来，人们从理论上和实验上广泛地研究了azulene的S_1-S_0内转化。在本研究中，我们首先指出了azulene在CIX上具有非平面结构。我们还考察了取代基对偶氮烯内部转化过程的影响。

The π conjugated molecules, which exhibit a wide variety of photochemical behaviors, have been of great interest in experiments and theory. In spite of much effort to elucidate the photochemical behaviors, however, most of them have not been reasonably interpreted yet.In this research project, we theoretically examined the photochemistry of diarylethenes which are much expected as a molecular photo-memory. We also examined the photochemistry of another π conjugated system of azulenes. Actual results of each research theme are as follows.1) Conical intersection (CIX) for the photocyclization of diarylethene.The CIX is the most important ingredients to understand the photochemistry of diarylethene. In the present CASSCF calculation, it is found that the CIX has no symmetry, while both reactant and product has C_2 symmetry.1) S_1-S_0 internal conversions of azulenesAzulene is a well-known molecule which violates Kasha's rule. For 50 years, the S_1-S_0 internal conversion of azulene has been extensively examined experimentally and theoretically. In the present study, we first pointed out that azulene takes a non-planar structure at the CIX. We also examined the substituent effect on the internal conversion process of azulenes.