Säurestärke und Komplexbildung von Curcuminoiden

Abstract

Acidity and Complex Formation of Curcuminoids The stoichiometric acid dissociation constants of curcumin 1a and derivatives as well as the stoichiometric stability constants of the Cu(II)‐ and Ni(II)‐complexes of these substances have been determined by pH‐potentiometric titrations in dioxane‐water mixture. The influence of different substituents on the pK a ‐values and the stability constants is discussed. The complexing properties of the COCH 2 CO structural element of the ligands are not significantly changed when the phenyl group is substituted by the styryl group. Solid CuL 2 ‐complexes have been characterized. The coordination of the ester group in the tricarbonyl ligand systems 4 was excluded by i.r. spectroscopy.