Metal–organic coordination architectures of condensed heterocyclic based 1,2,4-triazole: Syntheses, structures and emission properties

Abstract

In efforts to explore the effects of metal ions, ligand structures, counteranions on the structures and properties of metal–organic complexes, seven d10 metals (Zn and Cd) and transition metals (Cu and Co) coordination compounds with condensed heterocyclic based 1,2,4-triazole 4,7-diphenyl-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (L1), 4-phenyl-7-(pyridine-3-yl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (L2), 4-phenyl-7-(pyridine-4-yl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (L3), and 4-(pyridine-3-yl)-7-(pyridine-4-yl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole (L4), Zn(L1)2Cl2 (1), Co(L1)2Cl2 (2), {[Cd(L2)2(H2O)2]·(ClO4)2}∞ (3), Cd(L2)2(NO3)2(H2O)2 (4), {[Cu(L3)2(NO3)2]·(CH2Cl2)}∞ (5), {[Cu(L3)2(OH)(MeOH)]·(MeOH)2·BF4}∞ (6) and [Cd(L4)2(NO3)2]∞ (7) were synthesized and structurally characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction. Complexes 1, 2 and 4 have a mononuclear structure, 1 and 2 have similar structure, 3 and 6 have a neutral rhombohedral grid with a (4,4) topology, the coordination network of 3 further assembled into a three-dimensional framework by O–H⋯O hydrogen-bonding interactions, 5 reveals a coordination chain structures consisting of a neutral chain {[Cu(L3)2(NO3)2]·(CH2Cl2)}∞ with the CuII centers, and 7 has a coordination chain. Obviously, the structural differences among them are attributable to the difference of metal ions, counter-anions, the locality and amount of coordination atoms in ligands framework. All the complexes are air stable at room temperature. Furthermore, the fluorescent properties of complexes 1, 3, 4, 7 and corresponding ligands have been investigated and discussed.