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

Erçag Ayse (Istanbul University, Engineering Faculty, Department of Chemistry, Istanbul, Turkey)
Sismanoglu Tuba (Istanbul University, Engineering Faculty, Department of Chemistry, Istanbul, Turkey)
Pura Suheyla (Istanbul University, Engineering Faculty, Department of Chemistry, Istanbul, Turkey)

The stability constants of the 1:1 binary complexes of Ni(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 (NaClO4) in aqueous solutions at 15.0 and 25.0 ºC. The thermodynamic parameters ΔGf0, ΔHf0 and ΔSf0 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.

Keywords: leucine, glutamic acid, amitrole, binary and ternary complexes