Graduate School of Material Science, University of Hyogo^* Graduate School of Material Science, Osaka City University^**
○Kimihiro Kimura^* Yoshiki Ozawa^* Minoru Mitsumi^* Koshiro Toriumi^* Isamu Kinoshita^**

Hexanuclear 6-methyl-2-pyridinethiolato copper(I) [Cu₆(6-mpyt)₆] crystals show highly luminescence whose color changes　from red (room temperature) to green-blue (liquid nitrogen temperature) with a decrease in temperature, i.e., luminescence thermochromism. The assignments of intense luminescence bands of these multinuclear-copper(I) compounds are complicated because weak interacted multi-copper centered (CC) transition is often concurrent with common Cu(I) to ligand charge transfer transition. We have tried direct observation of photo-induced geometrical change of the complex by using the photo exited state crystallographic technique in order to figure out the luminescence characteristics of this compound.
Single crystal X-ray diffraction experiments were performed by using the low-temperature vacuum X-ray camera at SPring-8 BL02B1 beamline. Full intensity data of both under light irradiated and non-irradiated conditions were collected at 25 K and 150 K by the multiple-exposure IP method. He-Cd CW laser (442 nm 100 mW, 325 nm 30 mW) was used for photo-excitation of the crystal. Photo-difference Fourier syntheses base on (|F_on|-|F_off|) show positive and negative peaks pairs around the Cu atoms. This result indicates that the trigonally compressed octahedral Cu₆ core is shrank toward perpendicular to the -3 axis.
[1]H.Xie et al., J.Phys.Chem.B, 2005, 109, 9339-9345.
[2]Y.Ozawa et al., Chem.Lett., 2003,32, 62-63.