Studies of copper(II) chelates ofo-hydroxyacetophenone and its substituted derivatives in dioxane-water mixtures

Summary The interactions of Cu^II witho-hydroxyacetophenone (OHA) and its halogeno- and nitro-substituted derivatives were investigated potentiometrically in dioxane-water mixtures by the Calvin-Bjerrum titration technique at 25° C and ionic strength =0.1 M (NaClO₄). All the ligands form 11 and 12 chelates with Cu^II.The variations of pK with mole fraction of dioxane and 1/D were almost linear. Linearity was observed in the plots of log K₁/logK₂ versus pK, and the magnitudes of slopes led to the conclusion that -donation is: (i) strong in aqueous medium and decreases with the increase in dioxane content in 11 chelates, and (ii) weak and does not change with dioxane, in 12 chelates.