A linear tetranuclear Cu(II) complex exhibiting both ferro and antiferromagnetic couplings: Synthesis, characterization and magneto-structural studies

Abstract

The pyrimidinyl hydrazone ligand OC{NHNC(Me)(pm)}2 (pm = 2-pyrimidinyl) (L3H2) has two potentially protic H atoms and multiple donor atoms. The reaction of L3H2 with CuCl2·2H2O yielded the tetranuclear complex [Cu4(L3H)2Cl6(CH3OH)2] (1). Structural studies on 1 reveal the molecule is located about a crystallographic inversion centre, affording two crystallographically independent Cu(II) centres with the two symmetry equivalent [Cu2(L3H)Cl3CH3OH] units connected via µ2-Cl bridges to generate a linear tetranuclear copper complex. The ligand is singly deprotonated (L3H−) and twisted around the diazine NN′ bond, affording an N3 donor set for the Cu1 centre and an N2O donor set for the Cu2 centre. The Cu1 ion is five coordinate with an [N3] donor set from the L3H− ligand and the remaining two sites occupied by Cl− anions. The Cu2 ion is six coordinate with the L3H− ligand offering a mer [N2O] donor set, with the three remaining sites occupied by two Cl− anions and a MeOH molecule. Magnetic studies reveal the presence of strong antiferromagnetic interactions via the diazine bridge linking the Cu1 and Cu2 ions and moderate ferromagnetic interactions via the chloro bridges located about the inversion centre, connecting the Cu2 and Cu2i ions.