Tricarbonylrhenium(I) complexes with heterodentate ligands based on functionalized amides: Synthesis, structural features, and cytotoxic activity

The reactions of 2-diphenylphosphorylaniline with 2-methylsulfanylbenzoyl chloride or 2-diphenylphosphinobenzoic acid in the presence of a coupling agent afforded new potentially tridentate ligands with different donor sets. Upon interaction with Re(CO)5Br, the compounds obtained formed either bidentately bound molecular or pincer-type tricarbonylrhenium(I) complexes depending on the reaction conditions. The resulting complexes were fully characterized in solution and in the solid state by multinuclear NMR and IR spectroscopy and, in most cases, by single-crystal X-ray diffraction. The preliminary evaluation of cytotoxicity of the complexes obtained against human colon (HCT116), breast (MCF7), and prostate (PC3) cancer cell lines revealed the high activity of κ3-S,N,O-pincer-type complex with ancillary S-donor group. The latter demonstrated considerable effect also on transformed breast cell line HBL100 and its doxorubicin-resistant subline HBL100/Dox.