Phenanthroline and phenyl carboxylate mixed ligand copper complexes in developing drugs to treat cancer

The success of a classic inorganic coordination compound, Cisplatin, cis-[Pt(NH₃)₂Cl₂], as the first anticancer metallodrug started a field of research dedicated to discovering coordination compounds with antitumor activity, encompassing various metals. Among these, copper complexes have emerged as interesting candidates to develop drugs to treat cancer. In this work, mixed ligand complexes of Cu(II) with diimines (phenanthroline or 4-methylphenanthroline) and 3-(4-hydroxyphenyl)propanoate, phenylcarboxylate or phenylacetate were synthesized. They were characterized in the solid state, including a new crystal structure of [Cu₂(3-(4-hydroxyphenyl)propanoate)₃(phenanthroline)₂]Cl·H₂O. The obtained complexes presented a variety of stoichiometries. In solution, complexes were partially dissociated in the corresponding Cu-diimine complex. The complexes bound to the DNA by partial intercalation and groove binding, as assessed by Circular Dichroism, relative viscosity change and UV–Vis titration. The cytotoxicity of the complexes was determined in vitro on MDA-MB-231, MCF-7 (human metastatic breast adenocarcinomas, the first triple negative), MCF-10A (breast nontumoral), A549 (human lung epithelial carcinoma), and MRC-5 (human nontumoral lung epithelial cells), finding an activity higher than that of Cisplatin, although with less selectivity.