Switching on Cytotoxicity of Water-Soluble Diiron Organometallics by UV Irradiation.

The diiron compounds [Fe 2 Cp 2 (CO) 2 (μ-CO)(μ-CSEt)]CF 3 SO 3 , [ 1 ]CF 3 SO 3 , K[Fe 2 Cp 2 (CO) 3 (CNCH 2 CO 2 )], K[ 2 ], [Fe 2 Cp 2 (CO) 2 (μ-CO)(μ-CNMe 2 )]NO 3 , [ 3 ]NO 3 , [Fe 2 Cp 2 (CO) 2 (PTA){μ-CNMe(Xyl)}]CF 3 SO 3 , [ 4 ]CF 3 SO 3 , and [Fe 2 Cp 2 (CO)(μ-CO){μ-η: 1 η 3 -C(4-C 6 H 4 CO 2 H)CHCNMe 2 }]CF 3 SO 3 , [ 5 ]CF 3 SO 3 , containing a bridging carbyne, isocyanoacetate, or vinyliminium ligand, were investigated for their photoinduced cytotoxicity. Specifically, the novel water-soluble compounds K[ 2 ], [ 3 ]NO 3 , and [ 4 ]CF 3 SO 3 were synthesized and characterized by elemental analysis and IR and multinuclear NMR spectroscopy. Stereochemical aspects concerning [ 4 ]CF 3 SO 3 were elucidated by 1 H NOESY NMR and single-crystal X-ray diffraction. Cell proliferation studies on human skin cancer (A431) and nontumoral embryonic kidney (HEK293) cells, with and without a 10-min exposure to low-power UV light (350 nm), highlighted the performance of the aminocarbyne [ 3 ]NO 3 , nicknamed NIRAC (Nitrate-Iron-Aminocarbyne), which is substantially nontoxic in the dark but shows a marked photoinduced cytotoxicity. Spectroscopic (IR, UV-vis, NMR) measurements and the myoglobin assay indicated that the release of one carbon monoxide ligand represents the first step of the photoactivation process of NIRAC , followed by an extensive disassembly of the organometallic scaffold.