Triiron Complex with N-Ferrocenyl Aminocarbyne Ligand Bridging a Diiron Core: DFT, Electrochemical, and Biological Insights

The first N-ferrocenyl aminocarbyne complex, [Fe2Cp2(CO)2(μ-CO){μ-CN(Me)(Fc)}]CF3SO3 ([2]CF3SO3), was synthesized with an 88% yield from [Fe2Cp2(CO)4], isocyanoferrocene (CNFc), and methyl triflate. The synthesis proceeded through the intermediate formation of [Fe2Cp2(CO)3(CNFc)], 1. Multinuclear NMR experiments revealed the presence of cis and trans isomers for [2]CF3SO3 in organic solvents, in agreement with DFT outcomes. Electrochemical and spectroelectrochemical studies demonstrated one reduction process occurring prevalently at the diiron core and one oxidation involving the ferrocenyl substituent. The oxidation process is expected to favor the redox activation of [2]+ in a biological environment. Both [2]CF3SO3 and its phenyl analogue [Fe2Cp2(CO)2(μ-CO){μ-CN(Me)(Ph)}]CF3SO3 ([3]CF3SO3), prepared for comparison, exerted moderate antiproliferative activity against the human cancer cell lines A431, HCT-15, PSN-1, 2008, and U1285. However, [2]CF3SO3 exhibited a higher cytotoxicity than [3]CF3SO3, showed a substantial ability to induce intracellular ROS production, and outperformed cisplatin in a three-dimensional SCLC cell model.