NNS tridentate thiosemicarbazide and 1,3,4-thiadiazole-2-amine complexes of some transition metal ions: syntheses, structure and fluorescence properties

The treatment of Hppts with conc. H 2 SO 4 formed N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-yl-amine ( 1 ).

Hppts is a nonfluorescent material, but 3 , 4 and the cyclized products 1,3,4-oxadiazole/1,3,4-thiadiazole are fluorescent. The cyclized ligand N-phenyl-5-(pyridin-2-yl)-1,3,4-thiadiazole-2-amine ( 1 ) formed [Zn(2-Hppt) 2 (OAc) 2 ] ( 6 ) and [Cd 2 (2-Hppt) 2 (OAc) 2 ( μ -OAc) 2 ] ( 7 ) in which Cd(II) has a binuclear acetate-bridged seven coordinate pentagonal bipyramidal geometry. Complex 7 is also a fluorescent material with maximum emission at 425 nm at an excitation wavelength of 254 nm.