Determination of Structure and Properties of Acetylacetone Dioxime, Benzoylacetone Dioxime and Bis‐Benzoylacetone Dioximato‐Copper (II): An Ultraviolet Study

Abstract

UV spectra of acetylacetone dioxime (2,4‐pentanedione dioxime = AADO), benzoylacetone dioxime (BADO) and bis‐benzoylacetone dioximato‐Cu(II) [Cu‐ (BADO*)2; BADO* = oxidized BADO] are recorded for aqueous and CHCl3 solutions at different pH values and interpreted. pKa values (1st dissociation constant) for AADO and BADO at constant ionic strenths (μ = 0.12) are derived: pKa (AADO) = 10.50; pKa (BADO) = 9.50, and the influence of molecular structure on acid‐base properties is discussed. Diagrams of possible molecular orbital energy‐level transitions for the oxime and the nitroso chromophores are given. The marked influence of acids (HC1) and bases (triethylamine, TEA) on the shape of the UV spectra of Cu‐ (BADO*)2 is discussed and explained in terms of the acid‐base properties of the nitroso and the oxime groups. Additional evidence has been adduced for the presence of nitroso group and of hydrogen bonds in these complexes.