Di- and tetranuclear heterometallic CuII-LnIII complexes (Ln = Gd and Dy): Synthesis, structure and magnetic properties

Four 3d–4f heterometallic complexes, [CuIILnIII(bpt)2(NO3)3(MeOH)] (Ln = Gd, 1; Dy, 2; bptH = 3,5-bis(pyrid-2-yl)-1,2,4- triazole), [CuII2LnIII2(µ-OH)2(bpt)4Cl4 (H2O)2]·6H2O (Ln = Gd, 3; Dy, 4), have been synthesized under solvothermal conditions. X-ray structural analyses reveal that 1 and 2 are isostructural while 3 and 4 are isostructural. In each complex, the copper and gadolinium or dysprosium ions are linked by two triazolate bridges and form a CuII-LnIII dinuclear unit. The intramolecular Cu-Ln distances are 4.542, 4.525, 4.545 and 4.538 Å for 1, 2, 3 and 4, respectively. Two dinuclear CuLn units are bridged by two OH− groups into the zig-zag tetranuclear {CuII2LnIII2} structures with the Ln(III)...Ln(III) distances of 3.742 and 3.684 Å for 3 and 4, respectively. Magnetic studies show that the antiferromagnetic CuII-LnIII interactions occur in 1 (JCuGd = −0.21 cm−1) and 2. The antiferromagnetic interaction occurs in complex 3 with JCuGd = −0.82 cm−1 and JGdGd = −0.065 cm−1, while dominant ferromagnetic interaction occurs in complex 4.