Synthesis, anticancer activity, and molecular docking of half-sandwich iron(II) cyclopentadienyl complexes with maleimide and phosphine or phosphite ligands

In these studies, we designed and investigated the potential Anticancer activity of five iron(II) cyclopentadienyl complexes bearing different phosphine and phosphite ligands. All complexes were characterized with spectroscopic analysis viz. NMR, FT-IR, ESI-MS, UV-Vis, fluorescence, XRD (for four complexes) and elemental analyses. For biological studies, we used three types of cells-normal peripheral blood mononuclear (PBM) cells, leukemic HL-60 cells and non-small-cell lung Cancer A549 cells. We evaluated cell viability and DNA damage after cell incubation with these complexes. We observed that all iron(II) complexes were more cytotoxic for HL-60 cells than for A549 cells. The complex CpFe(CO)(P(OPh)₃)(η¹-N-maleimidato) 3b was the most cytotoxic with IC₅₀ = 9.09 µM in HL-60 cells, IC₅₀ = 19.16 µM in A549 and IC₅₀ = 5.80 µM in PBM cells. The complex CpFe(CO)(P(Fu)₃)(η¹-N-maleimidato) 2b was cytotoxic only for both Cancer cell lines, with IC₅₀ = 10.03 µM in HL-60 cells and IC₅₀ = 73.54 µM in A549 cells. We also found the genotoxic potential of the complex 2b in both types of Cancer cells. However, the complex CpFe(CO)₂(η¹-N-maleimidato) 1 which we studied previously, was much more genotoxic than complex 2b, especially for A549 cells. The plasmid relaxation assay showed that iron(II) complexes do not induce strand breaks in fully paired ds-DNA. The DNA titration experiment showed no intercalation of complex 2b into DNA. Molecular docking revealed however that complexes CpFe(CO)(PPh₃) (η¹-N-maleimidato) 2a, 2b, 3b and CpFe(CO)(P(OiPr)₃)(η¹-N-maleimidato) 3c have the greatest potential to bind to mismatched DNA. Our studies demonstrated that the iron(II) complex 1 and 2b are the most interesting compounds in terms of selective cytotoxic action against Cancer cells. However, the cellular mechanism of their Anticancer activity requires further research.