Structure of a Terbium(III)−Quinizarine Complex: The First Crystallographic Model for Metalloanthracyclines

The crystal structure of a complex of terbium(III) with quinizarine
2-sulfonate has been solved by single-crystal X-ray diffraction
methods. The metal cation is coordinated by two adjacent
phenolate and quinone oxygens of the anthraquinone moiety of a
quinizarine sulfonate anion and by six water molecules. To our
knowledge, this is the first structure of a metal complex of the
1,4-dihydroxy anthraquinone ligand. On the basis of strict similarities
in the spectroscopic features of the terbium adducts with either
doxorubicin or quinizarine 2-sulfonate, the present structure is
proposed as a model for the metal complexes of anthracyclines.