The Synthesis of New Triazole Ligands and Determination of Complex Stability Constants with Transition Metal Cations in Aqueous Media

Six new triazole compounds were synthesized. These compounds containing the substituted benzylidenamino group were obtained by reaction of 3-(pyridine-4-yl)-5-p-tolyl-4-amino-4H-1,2,4-triazole 1 with the corresponding aldehyde. The reduced forms were prepared with NaBH4 in methanol. The structures of the compounds were determined by IR, H-1 NMR, and C-13 NMR spectral data, and their interaction with cations such as Li+, Na+, K+, Rb+, Cs+, Ba2+ Sr2+, Ca2+, Cu2+, Cr3+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+ and Ag+ were investigated by using UV-visible spectrophotometry. Of the tested metal cations, Cu2+, Cr3+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+ and Ag+ complexed with the ligands. The complex stability constants (log(10) K) were measured in slightly acidic aqueous media at 25.0 +/- 0.1 degrees C. These stability constants were determined by measuring the increase in solubility of the nearly insoluble ligand molecule due to complex formation with a soluble cation, and this method is discussed. It was found that the position of chlorine atoms on the benzene ring strongly affects the complexation of Cu2+ ion with these ligands.