Syntheses, Structures And Properties Of Mental Complexes Constructed By Thiadiazoles And Carboxylic Acids

In this paper, five new 1,3,4- thiadiazole derivatives have been successfully synthesized. By the assembling of the synthesized ligands or other polypyridyl and polycarboxylate based ligands with metal salts, two series of supramolecular complexes have been obtained at room temperature or under solvent thermal conditions and structurally characterized by elemental analyses, IR, TG-DSC and single crystal X-ray diffractions. The synthesis conditions of these complexes were studied, and the biological activity, fluorescence properties, magnetic and thermal behaviors as well as thermal decomposition kinetics of the complexes have also been investigated.Firstly, three complexes II 1-3 have been synthesized by treatments of the synthesized ligand, 5-ethyl-2-amino-1,3,4- thiadiazole (EATZ), with Zn( II), Cu( II), Cd( II) metal ions. For complexes II 1-3, biological activity study shows that all of them have good antimicrobial activities against Staphylococcus aureus. Moreover, complexes II 1 and II 3, which are constructed by metal ion with d¹⁰ electronic configuration, have special thermal decomposition mode of simple Prout-Tompkins equation and nth-order reaction with autocatalysis, respectively. The main decomposition process of these two complexes proceeds very fast and can be finished within the temperature range of 5 °C . Using 3-methyl-6-phenyl-[1,2,4]-triazole [3,4-b][l,3,4] thiadiazole (TRTZ) as the ligand, we obtain complexes II 4 and II 5, in which Ï€-Ï€ stacking exists widely between the conjugate rings of ligand TRTZ, through which the supramolecular structure are stabilized and formed.Secondly, by the reactions of the synthesized ligand, 2,6-di(N,N'-5-ethyl -1,3,4-thia-diazole-2-formamide)-pyridine (BTZPY), with different wetal ions, we obtain 13 complexes 1111-13, in which the BTZPY acts as bidentate, tridentate, tetradentate, penta-dentate and hexa-dentate ligands, respectively. III 1 is a hexanuclear complex containing a [Zn6(μ4-O)₂] core which is formed from two edge-shared tetrahedron and the ligands chelate Zn atom with penta-dentate coordination mode. III4 is a pentanuclear complex with μ₃-oxygen atoms in the metal polyhedrons and the five metal centers arrange in two triangles having one common vertex. BTZPY in this complex acts as tetradentate, penta-dental and hexa-dentate ligands, respectively. Unlike above mentioned complexes, III5 is a two-dimensional network polymer linked by coordinating bond and BTZPY acts as bi-dentate ligand bridging two different metals chains. We also have explored the photo-luminescent properties of III1, 2, 5, and the results indicate that the fluorescent property of III 1, 2 is induced by intermolecular charge transfer, and the fluorescent property of III 5 is assigned to ligand-to-metal charge transfer(LMCT). Complexes III2, III3, III6, III7 and III 12 are all trinuclear complex containing triangle frames formed by three metal ions which are bridged...