CRYSTAL AND MOLECULAR-STRUCTURE AND MAGNETIC-PROPERTIES OF A NEW MU-OXALATO BINUCLEAR COPPER(II) COMPLEX CONTAINING MEPIRIZOLE

The crystal and molecular structure of the new mu-oxalato binuclear copper(II) complex [(mpym)(H2O)(NO3)Cu(C2O4)Cu(NO3)(H2O)(mpym)].2H2O 1 [mpym = mepirizole = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine] has been determined by X-ray diffraction methods. It consists of discrete binuclear entities where the copper atoms lie in a strongly elongated octahedral environment, surrounded by two nitrogen atoms (one from each ring of a mepirizole molecule) and two oxygen atoms of the bridging oxalato group in the equatorial plane and oxygen atoms of water molecules and nitrate ions in the axial positions. The binuclear entities are not centrosymmetric and the difference in the ligand environments of the copper(II) ions induces an energy separation between the two magnetic orbitals large enough to weaken the antiferromagnetic interaction (J = -142 cm-1) by approximately 60 cm-1 compared to that of symmetrical mu-oxalato binuclear copper(II) compounds. ESR, virational and electronic spectra are consistent with the above results.