Electronic absorption spectra and tautomerism of quinizarin and its substituted derivatives

According to the data of quantum-chemical calculations and correlation analysis, the experimental electronic absorption spectra of quinizarin and its substituted derivatives contain bands corresponding to 9,10-, 1,10-, and 1,4-anthraquinoid tautomers. Analysis of the absorption spectra revealed specific features of the tautomeric structure of substituted quinizarins.