Ferrocene–Diiron(I) Bis(cyclopentadienyl) Conjugates Exhibit Potent In Vitro Cytotoxicity and Selectivity toward Cancer Cells Associated with ROS Scavenging

Eleven new triiron compounds were synthesized in 25–90% yields from [Fe2Cp2(CO)2(μ-CO){μ-CNMe(Fc)}]+, Fc = CpFe(η5-C5H4), through substitution of one or both terminal CO ligands, or alkyne-coupling with the bridging aminocarbyne to afford vinyliminium derivatives. Products were characterized by IR and multinuclear NMR spectroscopy, and in selected cases by cyclic voltammetry, single crystal X-ray diffraction and DFT calculations. The compounds exhibited near millimolar water solubility, Log Pow values between −0.7 and >1.5, and notable stability in physiological-like solutions. They displayed potent cytotoxicity against five cancer cell lines with IC50 values reaching the nanomolar range, combined with high selectivity over normal fibroblasts. The mode of action appears linked to a marked decrease in intracellular reactive oxygen species. Fluorimetric studies on a representative complex revealed a low tendency to bind bovine serum albumin (EB) and a moderate ability to interact with DNA.