Quantum-chemical and correlation study of ionization of Alizarin.

According to the results of quantum-chemical and correlation studies, ionized states of Alizarin and Alizarin Red are contributed mainly by tautomeric anthraquinoid structures. The probability of their formation increases due to solvation. The experimental electronic absorption spectra of the corresponding anions contain bands typical of the 2,9-, 1,10-, and 1,2-anthraquinoid tautomers. The 9,10-anthraquinoid structure of the anions is less probable. [ABSTRACT FROM AUTHOR]