Synthesis, Structures And Properties Of 1,3,4-Oxadiazole/Thiadiazole Derivatives And Their Transition Metal Complexes

The design and construction of metal complexes has been attracting enormous interest in coordination chemistry,not only because of its rich and colorful crystal structure,but also its potential applications in the fields of medicine,photoelectric and catalysis.Therefore,the design and synthesis of a series of 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives and their metal complexes have great significance and potential applications.The main contents of this paper are as follows:2,5-Dipyridyl-1,3,4-oxadiazole and 2,5-Dipyridyl-1,3,4-thiadiazole were synthesized for improving the biological activities and coordinations modes.The ligands L~1 [2,5-Di(2-pyridyl)-1,3,4-oxadiazole] and L~2 [2,5-Di(2-pyridyl)-1,3,4-thiadiazole] were synthesized from picolinic acid through esterification reaction,hydrazine decomposition,substitution reaction and ring-closing reaction using the technique of the Microwave irradiation and cyclodehydration of diacylhydrazide.The intermediates and products were characterized by 1HNMR,IR and XRD.The single crystal structure of V-shaped neutral L~2 showed that its crystallizes in the monoclinic with space group P21/n.The ligand L~2 form a three dimensional network structure due to the hydrogen bond effects and ?-? stacking interactions.The single crystal structure and coordination environment of ligand L~1 are similar to L~2.A series of transition metal complexes have been synthesized by the reactions of L~1 or L~2 with Fe(~?),Co(~?)and Ni(~?)in the presence of tetrafluoroborate or chlorate.Fortunately,the binuclear metal complexes [1:2(ligand : metal)] Co2(bpod)(H2O)5(Cl)4 and Ni2(bpod)(H2O)6(Cl)4 were obtained by the reactions of L~1 with Cobalt(?)chloride or Nickel(?)chloride in the ethyl alcohol.All of the nitrogen atoms within the ligand L~1 take part in coordination.In addition,the coordination property of ligand L~2 was also been studied.The structures of all complexes were characterized by 1HNMR,IR and XRD.The properties of complexes have also been discussed by the magnetic analysis,UV,TGA and fluorescence analysis.