Studies on the formation of a complex of Cu(II) with sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate – An analogue of the core unit of anthracycline anticancer drugs and its interaction with calf thymus DNA

Copper(II) forms a complex with sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (sodium quinizarin-2-sulphonate, NaQSH2), an analogue of the core unit of anthracycline antibiotics used in the treatment of cancer. The 1:2 metal–ligand complex is formed in aqueous solution at neutral and acidic pH while in alkaline pH both 1:1 and 1:2 species are formed. The effective stability constant of the 1:2 metal–ligand complex is 9.64 × 1016 while that of the 1:1 metal–ligand complex is 9.4 × 109. The 1:2 complex Cu(NaQSH)2(H2O)2 was synthesized and characterized by different techniques in solid state and in solution. The complex Cu(NaQSH)2(H2O)2 interacts with calf thymus DNA which was studied by fluorescence spectroscopy. The binding constant and site size for the interaction with DNA were determined.