EQUILIBRIUM STUDIES ON THE FORMATION-CONSTANTS OF SOME NEWLY SYNTHESIZED SUBSTITUTED MERCAPTOTRIAZOLES WITH CO(II), NI(II), CU(II) AND ZN(II)

Proton-ligand and metal-ligand formation constants of binary complexes of some newly synthesised 3-aryl-5-mercapto-4-(2-nitrophenyl)-1,2,4-triazoles (A) with Co(II), Ni(II), Cu(II) and Zn(II) ions (M) have been determined, where aryl group is phenyl (PMNPT), 4-chlorophenyl (PCPMNPT), 4-nitrophenyl (PNPMNPT), 2-nitrophenyl (ONPMNPT) and 3,5-dinitrophenyl (MDNPMNPT). Equilibrium studies have been also carried out on mixed ligand complexes of Cu(II) with ligands (A) and L [L = glycine (gly), beta-alanine (beta-ala), 1,10-phenanthroline (1,10-phen) and malonic acid (mal)] which act as NO, NN and OO donors respectively. Formation constants of both binary 1:1 (MA), 1:2 (MA2) and ternary 1:1:1 (MLA) complexes have been determined at 30-degrees-C in 70% (v/v) aqueous dimethylformamide (DMF) and I = 0.1 M (KNO3). The order of basicities is: ONPMNPT > MDNPMNPT > PMNPT > PCPMNPT > PNPMNPT. The stabilities log (beta) of metal complexes are in the order: Cu(II) > Ni(II) > Co(II) > Zn(II) with respect to metal ions and the order with respect to ligands is: MDNPMNPT > ONPMNPT > PMNPT > PCPMNPT > PNPMNPT. The stabilities of ternary complexes are low as compared to stabilities of corresponding binary complexes which may be explained on the basis of statistical factors.