Metal complexes with 1-hydroxyanthraquinone and its derivatives: Electronic absorption spectra and ligand structures

Reactions of metal salts with 1-hydroxyanthraquinone and its derivatives gave tautomeric 9,10-and 1,10-quinoid complexes and compounds containing no C=0 → M coordination bond. Each form is characterized by a single π1,π*-band. The absorption bands were assigned by using correlations with the σA-constants of the hydroxy and oxido groups for tautomeric anthraquinones. Complexes with nonionized ligands have particularly the 9,10-anthraquinoid structures; complexes with ionized ligands can form both 9,10-and 1,10-quinoid structures.