A quantum-chemical and correlation study of ionization of α,α′-dihydroxyanthraquinones

The participation of states with the predominant contribution of tautomeric anthraquinoid resonance structures in ionization of 1-hydroxy- and 1,4-, 1,5-, and 1,8-dihydroxy-9,10-anthraquinones was demonstrated by quantum-chemical and correlation methods. Solvation increases the probability of formation of such structures. The bands corresponding to anthraquinoid tautomers were revealed in the experimental absorption spectra of the ionized compounds. Published data on the pH dependence of the ratio of neutral molecules, monoanions, and dianions, obtained without taking into account tautomeric structures, require revision.