Abstract

Coordination of ternary complexes of biologically active ligands with transition metals were investigated in aqueous media at 37 ±1 ^oC under ionic strength I = 0.1 M NaNO₃. Amino acid asparagine (primary ligand =A) and nucleic acid thiouracil (secondary ligand=B) were applied for complex formation with Cu(II), Ni(II), Zn(II) and Co(II) in aqueous solution (1:1:1). The plausible equilibria have been deduced on the basis of speciation curves obtained through BEST computer program and species are also presented and discussed. The Protonation constant and metal ligand stability constant has been determined through the method suggested by Irving & Rossotti and further refined through BEST computer program. The mixed ligand ternary complexes were occurring simultaneously in most cases generally at high pH with gradually declination of binary complexes of particular metal complexes. The order of mixed ligands ternary system were found A-Cu(II)-B>A-Ni(II)-B> A-Zn(II)-B> A-Co(II)-B. The percentage of species formation curves have been demonstrated with the help of computer program ORIGIN 6.1 and possible structure of metal complexes with said ligands have been discussed

Keywords

Solution equilibria, Stability constants, Transition metals