Influence of secondary ligands on the stability of metal–xanthosine complexes in solution
Abstract
Potentiometric equilibrium measurements have been carried out at 35 °C for the formation of ternary complexes of xanthosine and CuII, NiII, ZnII, CoII, MnII, MgII, and CaII with histidine, catechol, and oxalic acid in a 1 : 1 : 1 ratio. The ternary complexes of these systems are more stable than the corresponding binary complexes. This increased stability is measured in terms of Δlog K. The Δlog K values for the 1 : 1 : 1 complexes of metal–xanthosine with aromatic ligands were found to be more positive (i.e. more stable) than those of the corresponding complexes with aliphatic ligands. This has been attributed to the ‘stacking phenomenon’ that occurs between the two aromatic moieties of the ligands in solution.