Structures, magnetic and thermal properties of polynuclear complexes built by pyridine-2,6-dicarboxylic acid-based multi-dentate ligand

By the reactions of a new ligand, 2,6-di(N,N′-5-ethyl-1,3,4-thia-diazole-2-formamide)pyridine (H2L), with Mn(II) and Cu(II) ions, two complexes namely [Mn3(μ3-O)(H2L)(L)2]·2DMF (1) and [Cu2(μ-H2O)(L)2]·DMF (2) were obtained, respectively. Compound 1 is a trinuclear complex containing triangle frames formed by three Mn(II) ions with a bridged μ3-O in the center; ligand H2L acts as a penta-dentate fashion. Compound 2 is a dinuclear complex, in which H2L coordinates two Cu(II) centers as a tetra-dentate coordination mode. Magnetic investigations show that an antiferromagnetic coupling between metal ions exists in 1, and a ferromagnetic coupling exists in 2. Thermal decomposition kinetic parameters of complex 1 are also obtained by employing non-isothermal (model-free) method.