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Huge Dielectric Response and Molecular Motions in Paddle-Wheel [CuII2(Adamantylcarboxylate)4(DMF)2]⋅(DMF)2

Authors

  • Dr. Qiong Ye,

    Corresponding author
    1. Ordered Matter Science Research Center, Southeast University, Nanjing 211189 (P.R. China)
    2. Research Institute for Electronic Science, Hokkaido University, N20W10 kita-ku, Sapporo 001-0020 (Japan)
    • Ordered Matter Science Research Center, Southeast University, Nanjing 211189 (P.R. China)
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  • Kiyonori Takahashi,

    1. Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan)
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  • Dr. Norihisa Hoshino,

    1. Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan)
    2. Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan), Fax: (+81) 22-217-5655
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  • Dr. Takemitsu Kikuchi,

    1. Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan)
    2. Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan), Fax: (+81) 22-217-5655
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  • Prof. Tomoyuki Akutagawa,

    Corresponding author
    1. Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan)
    2. Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan), Fax: (+81) 22-217-5655
    • Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan)
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  • Prof. Shin-ichiro Noro,

    1. Research Institute for Electronic Science, Hokkaido University, N20W10 kita-ku, Sapporo 001-0020 (Japan)
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  • Prof. Sadamu Takeda,

    1. Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)
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  • Prof. Takayoshi Nakamura

    Corresponding author
    1. Research Institute for Electronic Science, Hokkaido University, N20W10 kita-ku, Sapporo 001-0020 (Japan)
    • Research Institute for Electronic Science, Hokkaido University, N20W10 kita-ku, Sapporo 001-0020 (Japan)
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Abstract

The temperature-dependent dynamic properties of [CuII2(ADCOO)4(DMF)2]⋅(DMF)2 (1) and [CuII2(ADCOO)4(AcOEt)2] (2) crystals were examined by X-ray crystallography, 1H NMR spectroscopy, and measurements of the dielectric constants and magnetic susceptibilities (ADCOO=adamantane carboxylate, DMF=N,N-dimethylformamide, and AcOEt=ethyl acetate). In both crystals, four ADCOO groups bridged a binuclear CuII[BOND]CuII bond, forming a paddle-wheel [CuII2(ADCOO)4] structure. The oxygen atoms of two DMF molecules in crystal 1 and two AcOEt molecules in crystal 2 were coordinated at axial positions of the [CuII2(ADCOO)4] moiety, forming [CuII2(ADCOO)4(DMF)2] and [CuII2(ADCOO)4(AcOEt)2], respectively. Two additional DMF molecules were included in the unit cell of crystal 1, whereas AcOEt was not included in the unit cell of crystal 2. The structural analyses of crystal 1 at 300 K showed three-fold rotation of the adamantyl groups, whereas rotation of the adamantyl groups of crystal 2 at 300 K was not observed. Thermogravimetric measurements of crystal 1 indicated a gradual elimination of DMF upon increasing the temperature above 300 K. The dynamic behavior of the crystallized DMF yielded significant temperature-dependent dielectric responses in crystal 1, which showed a huge dielectric peak at 358 K in the heating process. In contrast, only small frequency-dependent dielectric responses were observed in crystal 2 because of the freezing of the molecular rotation of the adamantyl groups. The magnetic behavior was dominated by the strong antiferromagnetic coupling between the two S=1/2 spins of the CuII[BOND]CuII site, with magnetic exchange energies (J) of −265 K (crystal 1) and −277 K (crystal 2).

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