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

The complex Cu2(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 Cu2(O2CR)4L2 dimer structure. trans-2-Butenoate groups in molecules related by a center of symmetry have a short contact between the α-carbon atoms (3.611 Å), suggesting a study of the solid-state reactivity of this complex. Irradiation of the complex (60Co 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/kB=−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.