title: Intrinsic carrier doping in antiferromagnetically interacted supramolecular copper complexes with (pyrazino)tetrathiafulvalene (pyra-TTF) as the ligand, [CuIICl2(pyra-TTF)] and (pyra-TTF)2[CuI3Cl4(pyra-TTF)].
abstract: New supramolecular copper complexes with pyrazinotetrathiafulvalene (pyra-TTF) as the ligand, [Cu(II)Cl2(pyra-TTF)] (1) and (pyra-TTF) 2[Cu(I)3Cl4(pyra-TTF)] (2), have been synthesized by the diffusion method. Complex 1 is a black block crystal with a three-dimensional (3-D) supramolecular network; the linear chain [-Cu(II)Cl2-(pyra-TTF)-] n extends along the b axis, where the coordinated pyra-TTF donors are stacked in a head-to-tail and ring-over-bond configuration to construct two-dimensional (2-D) sheets, and between the sheets, there are C...Cl(-) or H...Cl(-) contacts. Even though the electron spin resonance (ESR) measurement reveals the nearly Cu(II) state, complex 1 is a semiconductor with sigmaRT=1.0 x 10(-4) S cm(-1) and Ea=0.33 eV. The high-frequency conductivity measurement also confirmed the intrinsic slight carrier doping from Cu(II) to the pyra-TTF donor. This slight doping enhances not only the real and imaginary dielectric constants but also the antiferromagnetic interaction between Cu(II) spins following the 2-D Heisenberg model with 2J=-20 K. In contrast, complex 2 is a very thin black needle. This needle crystal has two crystallographically independent pyra-TTF molecules, which are coordinated and noncoordinated donors. The coordinated donors composed a supramolecular chain [Cu(I)3Cl4(pyra-TTF)(0)]n , whereas the noncoordinated donors formed conducting alpha''-type pyra-TTF(+0.5) sheets. This complex is semiconducting with sigmaRT=0.1 S cm(-1) and Ea=0.15 eV. Both complexes 1 and 2 demonstrate that the pyra-TTF molecule works not only as an oxidized donor by Cu(II) to construct conducting sheets but also as a ligand coordinated to a Cu cation to form supramolecuar chains.
authors.affiliation: The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan, and CREST-JST, Japan. ichikawa@issp.u-tokyo.ac.jp
authors.forename: Shun
authors.initials: S
authors.lastname: Ichikawa
authors.forename: Shinya
authors.initials: S
authors.lastname: Kimura
authors.forename: Kazuyuki
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authors.lastname: Takahashi
authors.forename: Hatsumi
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authors.lastname: Mori
authors.forename: Gosuke
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authors.lastname: Yoshida
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Manabe
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsuda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tajima
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Yamaura