Structure and magnetic properties of binuclear Cu2(O2CCH=CHCH3)4(DMF)2:: a carboxylate-bridged Cu(II) spin dimer

The complex Cu-2(O2CCH=CHCH3)(4)(DMF)(2) was synthesized from Cu(OH)(2), trans-2-butenoic acid, and dimethylformamide. An X-ray structure determination showed that the complex has the familiar Cu-2(O2CR)(4)L-2 dimer structure, trans-2-Butenoate groups in molecules related by a center of symmetry have a short contact between the ct-carbon atoms (3.611 Angstrom), suggesting a study of the solid-state reactivity of this complex. Irradiation of the complex (Co-60 X-rays, 219 kGy), did not produce any detectable product. Magnetic susceptibility measurements in the range between 2 and 350 K in a powder sample, and EPR measurements in powder and single-crystal samples were performed. The data show the dimeric magnetic structure of the compound, with an antiferromagnetic exchange coupling J/k(B) = -220 K and a fine structure coupling D/h = -10.04 GHz within the excited spin triplet. Hyperfine structure with the two Cu nuclei is clearly observed. These results are discussed in terms of the structure. (C) 2000 Elsevier Science B.V. All rights reserved.