Ternary complexes of xanthosine in solution

Abstract

Stability constants, of the mixed ligand complexes (1:1:1) containing metal-xanthosine (1:1) [M=Cu(II), Ni(II), Zn(II), Co(II), Mn(II), Mg(II), and Ca(II)] complexes and secondary ligands. N,N-tetramethylethylenediamine (TMEN), α,α'-bipyridyl (bipy), 1-10-phenanthroline (O-Phen) and 5 sulfosalicylic acid (SSA) or metal-xanthosine in a 1:2 ratio, have been determined potentiometrically at 45±0.1°C and 0.10 M (KNO₃) ionic strength. The stability constants of these metal ternary complexes and 1:2 metal-xanthosine complexes are found to be higher than the corresponding stability constants of binary complexes. Thus the positive values of Δ log K (defined as the difference in the overall 1:1:1 stability constants and corresponding 1:1 binary complexes) may be due to the "stacking" interaction of the ligands concerned.