Solution and molecular modeling studies on some bivalent metal complexes of higher analogues of biologically active 1,3-diaryl-4, 5, 6-pyrimidinetrione- 2-thioxo-5-oxime

Abstract

Thermodynamic proton-ligand stability constants of 1,3-diethylphenyl-4,5,6- pyrimidinetrione-2-thioxo-5-oxime (and the thermodynamic metal ligand stability constants) with some bivalent metal ions were determined by potentiometric measurements in 75% (v/v) aqueous-dioxan medium at different temperatures ranging from 25° C to 35° C. The acidity and stability constants vary according to the kind of substitution at the 1- and 3- positions of the pyrimidine ring. The order of stability constants is UO₂²⁺> Cu²⁺>Ni²⁺>Co²⁺ >Zn²⁺ >Cd²⁺ >Mn²⁺ >Mg²⁺. The values of S_min (χ²) have also been calculated. The thermodynamic functions for the stepwise complexation processes are calculated at 25±0.5^oC. Molecular modeling studies have also been carried out on the ligand and complexes, the results of which corroborate the experimental findings.