Studies on Photo-excited State Crystal Structure of Multinuclear Metal Complexes by X-ray Structure Analyses.

利用同步辐射装置的单晶x射线结构分析，研究了发光多核金属配合物在光激发态下分子结构的几何变化。特别引入了激发光与x射线同步间断的装置，以抑制激光照射时晶体热负荷的影响。与未照射条件相比，光照射下的热量上升能够从25K或更多降低到5K左右。这样可以抑制晶体热膨胀引起的晶体结构变化，从而更准确地检测光激发引起的分子结构变化。结果总结如下：1。在蓝色激光（442nm）照射下，对铜(I)聚合物配合物[Cu_2I_2(PPh_3)_2(4,4′-bpy)]_∞进行了光激发结构分析。光差傅立叶合成表明，Cu_2I_2单元中两个I原子彼此靠近，而两个Cu原子彼此稍微分开，表明铜周围的配位环境由一价变为二价。这些几何变化是由于金属到配体的电荷转移（MLCT）。当远离MLCT波段的绿色激光（532 nm）照射时，没有观察到原子的这种运动。铑（III）配合物反式-[RhX_2(py)_4(BPh_4)] （X=Cl,Br，I; py=C_5H_5N）表现出d-d跃迁的发光现象。光激发结构分析表明，卤素原子的温度因子比其他原子的温度因子增加得更多。这种热运动的振幅在垂直于Rh-X键的方向上增强。结果表明，Rh-X键的弯曲运动降低了分子结构的对称性，从而稳定了d-d禁止电子迁移的光激发态。用x射线结构分析了[Rh(Cp'Rh)_2(CH_2)_2(O_2SSO_2) （Cp'=Me_5C_5）在室温和低温下晶态光异构化速率的时间依赖性。光产物的四种立体异构体中只有一种在室温下被发现，而所有的立体异构体都在低温下被观察到。这表明光产物的某些立体异构体可以通过热平衡转化为其他异构体。少

We have developed instrumentation and method for investigating geometrical change in molecular structure at photo-excited state of luminescent multi-nuclear metal complexes by using single crystal x-ray structure analyses at a synchrotron radiation facility. Especially, the device that synchronously intermitted the excitation light and X-rays was introduced to suppress the influence of the heat load of the crystal when the laser was irradiated. The rise in heat at the light irradiation comparing to non-irradiated condition was able to be decreased from 25K or more to around 5K. As a result, the crystal structure change by the thermal expansion of the crystal was suppressed, and the change in a molecular structure by photo-excitation can be detected more accurately. Summary of results is as follows :1.Photo-excited structure analyses of copper (I) polymer complex [Cu_2I_2(PPh_3)_2(4,4'-bpy)]_∞ have been performed under blue laser (442nm) illumination. Photo-difference Fourier syntheses … More revealed that two I atoms in a Cu_2I_2 unit approached close each other, while two Cu atoms moved slightly apart from each other, which suggest the coordination environment around copper is changed from monovalent to divalent. These geometrical changes due to metal-to-ligand charge transfer (MLCT). When green laser (532 nm), which is away from the MLCT band, was irradiated, this movement of the atoms is not observed.2.A rhodium (III) complex trans-[RhX_2(py)_4(BPh_4)] (X=Cl,Br,I ; py=C_5H_5N) shows a luminescence phenomenon assigned to the d-d transition. Photo-excited structure analyses showed that the temperature factor of the halogen atom increased more than other atoms in the light irradiations. The amplitude of this thermal motion is enhanced perpendicular to the Rh-X bond. The results suggested that bending motion of Rh-X bond decrease the symmetry of a molecular structure, which can stabilize the photo-excited state, derived from d-d prohibited electron migration.3.The time dependence of photo-isomerization rate in crystalline state at room temperature and low temperature of (Cp'=Me_5C_5) of [Rh(Cp'Rh)_2(CH_2)_2(O_2SSO_2) has been performed by X-ray structure analyses. Only one of four stereoisomers of the photoproducts is found at room temperature, while all stereo isomers are observed at the low temperature. This shows that the some stereo isomers of the photoproducts can be converted to other isomers via thermal equilibrium. Less