Syntheses, Crystal Structures, and Solid State Properties of Halogen-bridged mixed-valence siplatinum complexes PtィイD22ィエD2(RCSィイD22ィエD2)ィイD24ィエD2I

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Halogen-bridged mixed-valence diplatinum complexes PtィイD22ィエD2(RCSィイD22ィエD2)ィイD24ィエD2I (R= CHィイD23ィエD2 (1), CィイD22ィエD2HィイD25ィエD2 (2), n-CィイD23ィエD2HィイD27ィエD2 (3), n-CィイD24ィエD2HィイD29ィエD2(4)) with linear chain structures of repeating units {-I-Pt-Pt-} are particular interest because they are possible to take a variety of valence ordering. The crystals of 1 which was first reported by Bellitto et al. exhibit anomalous electrical conducting behavior (T < 300K, semiconductor ; 300 K < T < 340 K, metallic). The variable temperature crystal structure analyses revealed dynamic disorder of the ligands.In order to elucidate the relation between the solid state behavior and the valence ordering of Pt atoms on the linear chain, the compounds 2 - 4 were synthesized and their crystal structure analyses and electrical conducting measurements were carried out. The M-I transitions were observed for 2 and 4.Since the crystal structure analyses provided only the averaged structures, we tried to measure the diffuse scattering corresponding to low-dimensional valence ordering of Pt atoms. Single crystal X-ray photographs of the compounds 1 and 2 were taken at variable temperatures by using the vacuum type X-ray camera and SPring-8. It was revealed that although the diffuse scattering corresponding to the valence alternation along the linear chain have been observed for 2 above 200 K (metallic state), but changed to the Bragg spots below 100 K (semiconductive state).