Synthesis and Characterization of a Di-µ-oxalato Tetracopper(II) Complex with Tetranucleating Macrocyclic Ligand

A tetracopper(II) complex containing two oxalate anions in the metal-based host cavity, [Cu4(Lpy)(µ-ox)2](PF6)2·2(2-PrOH), where ox2−: oxalato (C2O42−), was prepared by reacting H2Lpy, a phenol-based tetranucleating macrocyclic ligand with four pyridylmethyl pendant arms, Cu(ClO4)2·6H2O, and sodium oxalate (1:4:2 stoichiometry, respectively) in methanol, followed by exchange of the counteranion with excess of NH4PF6. Single-crystal X-ray diffraction of 1revealed that two {Cu(II)Cu(II)} units, bridged by a phenolato group of Lpy2−, were connected by two oxalato anions, to construct a rectangular “{CuCu}(µ-ox)2{CuCu}” tetranuclear framework. This rectangular framework was maintained in DMF solution. The magnetic measurement of 1in the 2–300 K range revealed antiferromagnetic behavior. The antiferromagnetic interaction in this complex occurs between the Cu(II) centers bridged by an oxalate (J= −140 cm−1).