Modelling the Binding of Cytotoxic Dinuclear Copper Complexes to two Neighboring Phosphate Esters of DNA Using Glutarate: A Tetranuclear Metallo‐Macrocycle vs a Dinuclear Model

Abstract

AbstractA family of dinuclear complexes was rationally designed to bind to two neighboring phosphate diesters of DNA by molecular recognition. Although these complexes bind strongly and irreversibly to DNA and induce apoptosis in cancer cells, a direct proof of the intended binding mode is missing. To mimic two neighboring phosphate diesters of DNA, we use here the dicarboxylate glutarate as a difunctional ligand. Starting from the acetate‐bound CuII2 complex, protonation results in the de‐coordination of acetate and allows the synthesis of the glutarate‐bound complex. Instead of bridging two CuII ions of one dinuclear complex, two glutarates bridge two dinuclear complexes resulting in a tetranuclear metallo‐macrocycle. The molecular structures of two different salts differ in the square‐pyramidal coordination to the CuII ions. The carboxylate stretching modes, the d‐d and the CT transtitions are not sensitive enough to resolve these differences. The exchange coupling is weakly antiferromagnetic between the CuII ions in the dinuclear subunits and negligible between the subunits via the glutarates. The consequences for suited ligands to model the binding to two neighboring phosphate diesters in the DNA backbone is discussed.