Thermodynamics of binary and ternary complexes of 3-amino-1,2,4-triazole and amino acids with Ni(Ⅱ) and Co(Ⅱ) metal ions

摘要

The stability constants of the 1:1 binary complexes ofNi(Ⅱ) and Co(Ⅱ) with 3-amino-1,2,4-triazole (AT), leucine (Leu) and glutamic acid (Glu), and the 1:1:1 ternary complex of them and the protonation constants of the ligands were determined potentiometrically at a constant ionic strength of I= 0.10 mol L~(-1) (NaClO_4) in aqueous solutions at 15.0 and 25.0℃. The thermodynamic parameters ΔG_f~0, ΔH_f~0 and ΔS_f~0 are reported for the formation reactions of the complexes. The enthalpy changes of all the complexations were found to be negative but the entropy changes positive. While the driving force for the formation of the Ni(Ⅱ), Co(Ⅱ) - AT complexes is the enthalpy decrease, the driving force for the ternary complexes of AT is the entropy increase.