ハロゲン架橋一次元金属錯体における構造―物性相関

抄録

The series of halogen-bridged N^II-X-M^IV mixed valence compounds (M=Pt, Pd; X=Cl, Br, I) has attracted much interest from solid state physicists and chemists as one dimensional compounds having strong electron-lattice interactions. Their structures are well described as Peierls distorted linear chains with repeating unit…M^II…X-M^IV-X…. They show characteristic physical properties such as strong charge transfer absorption and luminescence with large Stokes shift that can be interpreted by using an extended Peierls-Hubbard model. The relation between the Peierls energy gap and lattice distortions for the compounds has been established by a number of structural and optical studies. The remarkable feature that the physical and structural parameters of the compounds can be controlled by changing chemical parameters such as central metals, bridging halogens, and counter ions has been also elucidated. From an expectation based on the relation, the halogen-bridged Ni^III-X-Ni^III compounds with an extreme limit of the M^II-X-M^IV compounds were synthesized. The novel structure having no Peierls distortion has been determined by detailed X-ray diffraction and physical studies. Further studies on the interesting physical properties such as an extremely strong antiferromagnetic coupling between electronic spins localized on the Ni^III atoms are now in progress.