| Budget Amount *help |
¥13,000,000 (Direct Cost: ¥13,000,000)
Fiscal Year 2004: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2003: ¥11,800,000 (Direct Cost: ¥11,800,000)
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| Research Abstract |
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
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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
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