Synthesis, crystal structure, magnetic study and magneto-structural correlation of three Cu(II) complexes formed via pyridine bis(hydrazone) based ligand

This report describes the synthesis and characterization of three different complexes of molecular formulae {[Cu6L2(ClO4)(4)(m-ClO4)(2)(H2O)(9)](ClO4)(2)center dot 8H(2)O}(n)(1), [Cu6L2Cl6(mu(2)-Cl)(2)(H2O)(2)]center dot 3H(2)O (2) and [Cu9L6](ClO4)(6)center dot 6H(2)O center dot 2CH(3)CN center dot CH3OH (3), where, H2L = bis[(2-pyridyl) methylene] pyridine 2,6 dicarbohydrazone. X-ray crystallography reveals that complex 1 exhibits 1D chain, complex 2 is a hexanuclear entity and an unsymmetrical [3 x 3] grid formation in complex 3. Variable temperature magnetic measurements were performed, they show that weak antiferromagnetic interactions exist among the metal centers in complex 1 and both ferro-and antiferromagnetic interactions coexist for complexes 2 and 3. Below 20 K antiferromagnetic interactions dominate for complex 2 whereas it is ferromagnetic for complex 3. Transformation from one cage to another is possible at mild reaction conditions, which results in a dramatic change in the magnetic properties.