Electrochemical studies of strongly chelating anthraquinone derivatives

TLDR: In this article, strongly chelating anthraquinones and their derivatives were studied by d.c. polarography, cyclic voltammetry and micro-coulometry to investigate their redox characteristics.

Abstract: Analytically important, strongly chelating anthraquinones and their derivatives were studied by d.c. polarography, cyclic voltammetry and micro-coulometry to investigate their redox characteristics. All 18 substances were reduced in a two-electron reversible or quasi-reversible process in both aqueous and 75% ethanolic solutions. Depending on pH and the medium, single or double polarographic reduction waves appeared, which were diffusion controlled, although in some instances adsorption pre-waves were also observed. This behaviour is similar to the known behaviour of simpler quinone systems. The variation of the Ilkovic coefficient and half-wave potential with pH was studied in detail to investigate the acid-base behaviour of the species involved in the reduction process. As a result, it was possible to describe the reduction mechanism of the anthraquinones involved.A number of new pK values were determined and others confirmed. Attempts to find linear free energy relationships were generally unsuccessful.