Mixed Copper Complexes of Some β-Diketones with α, α'-Dipyridyl

Cu-α, α'-dipyridyl (Cu-Dip) has two unoccupied coordination sites, and when acetylacetone, benzoylacetone, dibenzoylmethane, p-carboxydibenzoylmethane, trifluoroacetylacetone, benzoyltrifluoroacetone and salicylaldehyde were reacted on Cu-Dip respectively, the presence of two different equilibria in Chart 1 was suggested spectrophotometrically according to the ratio of Cu-Dip and β-diketone. These equilibria are : Cu-Dip+β-diketone⇄β-diketone-Cu-Dip, β-diketone-Cu-Dip+β-diketone⇄Cu (β-diketone)2+Dip. The isosbestic points which indicate the presence of the above equilibria respectively, were observed in the spectra of the mixed complexes. Furthermore, the study of the relation between the isosbestic points and β-diketone concentration to Cu-Dip revealed the relative reactivity for the formation of Cu(β-diketone)2 which was shown in the order : dibenzoylmethane>benzoylacetone>acetylacetone>salicylaldehyde>p-carboxydibenzoylmethane»trifluoroacetylacetone, benzoyltrifluoroacetone. Mixed complexes of Cu (II) with α, α'-dipyridyl and β-diketone (1 : 1 : 1) were synthesized by reacting β-diketone to Cu-Dip in 50% dioxane solution containing 0.1M NaHCO3.