Huge dielectric response and molecular motions in paddle-wheel [Cu II 2(Adamantylcarboxylate) 4(DMF) 2]a·(DMF) 2

Qiong Ye, Kiyonori Takahashi, Norihisa Hoshino, Takemitsu Kikuchi, Tomoyuki Akutagawa, Shin Ichiro Noro, Sadamu Takeda, Takayoshi Nakamura

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16 Citations (Scopus)


The temperature-dependent dynamic properties of [Cu II 2(ADCOO) 4(DMF) 2]â(DMF) 2 (1) and [Cu II 2(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 Cu II-Cu II bond, forming a paddle-wheel [Cu II 2(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 [Cu II 2(ADCOO) 4] moiety, forming [Cu II 2(ADCOO) 4(DMF) 2] and [Cu II 2(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 Cu II-Cu II site, with magnetic exchange energies (J) of -265 K (crystal 1) and -277 K (crystal 2).

Original languageEnglish
Pages (from-to)14442-14449
Number of pages8
JournalChemistry - A European Journal
Issue number51
Publication statusPublished - 2011 Dec 16


  • carboxylate ligands
  • copper
  • dielectric constants
  • metal-metal interactions
  • molecular devices


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