Synthesis, crystal structures and magnetic properties of the oxalate-bridged single CuIICuII and cocrystallized CuIIZnII systems. Three species (CuCu, CuZn, ZnZn) in the crystalline lattice

Abstract

Two novel oxalate-bridged species – homometallic CuIICuII, [{Cu(bpy)Cl}2(μ-C2O4)] (1) and heterometallic CuIIZnII, [CuZn{(bpy)Cl}2(μ-C2O4)] (2) (bpy=2,2′-bipyridine) – were synthesized and characterized by elemental analyses, IR and EPR spectroscopy, magnetic susceptibility measurements and single-crystal X-ray diffraction studies. The compounds crystallize in the same, triclinic P1¯ space group. Their crystal structures consist of the binuclear entities [M(bpy)Cl(μ-C2O4)M(bpy)Cl] [M=Cu2+ (1); M=Cu2+ and/or Zn2+ (2)] linked by the intermolecular π⋯π stacking interactions. Highly unusual, compound 2 is a cocrystallized system containing three types of mutually analogous entities: [Cu(bpy)Cl(μ-C2O4)Cu(bpy)Cl] (CuCu; the same unit as in 1), [Cu(bpy)Cl(μ-C2O4)Zn(bpy)Cl] (CuZn) and [Zn(bpy)Cl(μ-C2O4)Zn(bpy)Cl] (ZnZn), randomly distributed throughout the crystalline lattice in the molar ratio near to 1:2:1, respectively. Each metal atom in both 1 and 2 displays a square-pyramidal coordination involving two N atoms from the coordinated 2,2′-bipyridine ligand and two O atoms from the bridging oxalate group in the basal plane, and one chlorine atom in the apical position. Magnetization measurements, supported also by the EPR study, reveal a strong antiferromagnetic exchange interaction (J=−295(2) and −294(2)cm−1, for 1 and 2, respectively; H=−JS1·S2) between two copper(II) ions through the oxalate bridge.