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.