title: Electrical conducting bis(oxalato)platinate complex with direct connection of CuII ions.
abstract: Reactions of K1.62[Pt(ox)2].2H2O and [Cu(bpy)(H2O)3](NO3)2 yielded partially oxidized one-dimensional (1D) bis(oxalato)platinates of [Cu(bpy)(H2O)n]6[Pt(ox)2]7.7H2O (n = 2, 3, or 4) (1) and [Cu(bpy)(H2O)n]8[Pt(ox)2]10.8H2O (n = 3 or 4) (2). The average oxidation numbers of the platinum ions in 1 and 2 are +2.29 and +2.40, respectively. Complexes 1 and 2 crystallize in the triclinic P and monoclinic C2/c space groups, respectively, and the [Pt(ox)2]n- anions are stacked along the crystallographic b axis with 7-fold periodicity for 1 and 10-fold periodicity for 2. In 1, an oxalato ligand in the platinum chain directly coordinates to a paramagnetic [Cu(bpy)(H2O)3]2+ ion, whereas no such direct coordination was observed for 2. The electrical conductivity of 2 at room temperature along the platinum chain is approximately 3 orders of magnitude smaller (sigma||= 1.3 x 10(-3) S cm(-1)) than that of 1 (sigma|| = 0.9-0.5 S cm(-1)), and the activation energies of 1 and 2 are 29 and 67 meV, respectively. The longest inter-platinum distances in 1 and 2 are 2.762 and 3.0082 A, respectively, and this is responsible for the lower electrical conductivity of 2. An X-ray oscillation photograph taken along the b axis of 1 reveals the 7-fold periodicity in the 1D chain, consistent with the period of the Peierls distortion estimated from the degree of partial oxidation. The semiconducting state of 1 can therefore be regarded as a commensurate Peierls state. The magnetoresistance of 1 at ambient pressure indicates no interaction between conduction electrons in the platinum chain and local spins of the paramagnetic CuII ions. Application of hydrostatic pressures of up to 3 GPa enhances electrical conduction, as is often seen as the usual pressure effect on the electrical conductivity, which is due to enhanced orbital (Pt-5dz2) overlap by pressure application.
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Yamamoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nishikawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nihei
authors.forename: Takuya
authors.initials: T
authors.lastname: Shiga
authors.forename: Masato
authors.initials: M
authors.lastname: Hedo
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Uwatoko
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kitagawa
authors.forename: Yasujiro
authors.initials: Y
authors.lastname: Taguchi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Iwasa
authors.forename: Hiroki
authors.initials: H
authors.lastname: Oshio