Comparative Calorimetric and ¹H N.M.R. Studies of the Interaction of Ag(I) With a Series of Mixed-Donor Macrocycles Incorporating Nitrogen, Oxygen and or Sulfur Donor Atoms

Abstract

The interaction of silver ion with a range of mixed-donor macrocyclic ligands incorporating nitrogen, oxygen and/or sulfur donors has been investigated. Complementary calorimetric and n.m.r. studies in acetonitrile (and its deuterated derivative) were used to investigate the nature of the equilibria present as the metal/ ligand ratio was varied. In all systems the formation of a 1 : 1 species was observed, with a 1:2 (metal/ ligand ) species also being formed in the presence of excess ligand in the majority of cases. Enthalpies of formation for the various complexes have been determined. Stepwise stability constants for the respective [ AgL ]⁺ + L ↔ [AgL₂]⁺ equilibria have been estimated from the calorimetric titration data, and the factors promoting the formation of the 1:2 species are discussed. The studies confirm the enhanced affinity of Ag^I for thioether donors over ether donors.