Hg(II) complexes of 4-phenyl-5-(3-pyridyl)-1,2,4-triazole-3-thione and 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione and a Ni(II) complex of 5-(thiophen-2-yl)-1,3,4-oxadiazole-2-thione: Synthesis and X-ray structural studies

Abstract

Three new mixed ligand complexes, [Hg(en)(4-pptt)2] (2) {4-pptt=4-phenyl-5(3-pyridyl)-1,2,4-triazole-3-thione}, [Hg(en)(4-pot)2] (3) {4-pot=5-(4-pyridyl)-1,3,4-oxadiazole-2-thione} and [Ni(en)2(5-thot)2] (4) {5-thot=5-(thiophen-2-yl)-1,3,4-oxadiazole-2-thione}, have been prepared containing en as a co-ligand. It is observed that 5-(pyridine-4-carbonyl) hydrazine carbodithioic acid methyl ester undergoes cyclization during complexation with Hg(II) in the presence of ethylenediamine and formed complex 3 containing 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione. The metal complexes have been characterized with the aid of elemental analyses, IR, magnetic susceptibility and single crystal X-ray studies. The ligand 4-pptt (1) and complexes 2, 3 and 4 crystallize in the monoclinic system, space group P21/n, P21/c, P121/c1 and P21/n respectively. The ligand is present in the deprotonated thiol form in complexes 2 and 3, and is bonded covalently through sulfur, while in complex 4 the ligand 5-(thiophen-2-yl)-1,3,4-oxadiazole-2-thione is present as the thione form and is bonded to Ni(II) through the oxadiazole nitrogen. Complex 4 shows quasi-reversible redox behavior assignable to a Ni2+/Ni3+ one electron transfer. The photoluminescence properties indicate that the complexes are fluorescent materials with maximum emissions at 433, 376 and 465nm for complexes 2, 3 and 4 at excitation wavelengths of 293, 273 and 327nm, respectively. All the complexes contain extended hydrogen bonding that provides a supramolecular framework.