We recently reported the dual (antihormonal and cytotoxic) functionality of ferrocifens, which are organometallic complexes derived from hydroxytamoxifen, the standard molecule in the treatment of hormone-dependent breast cancers. To test the hypothesis that the presence of a ferrocenyl substituent on molecules with an affinity for the estrogen receptor is sufficient to give them cytotoxic properties in vitro, we prepared complexes derived from estradiol with a ferrocenyl substituent at positions 7alpha and 17alpha. The complexes thus obtained retain a satisfactory level of affinity for the estrogen receptor (RBA values higher than 12 %). At low concentrations (0.1-1 microM) the complexes show an estrogenic effect in vitro equivalent to that of estradiol on hormone-dependent (MCF-7) breast cancer cells, and no cytotoxic effect on hormone-independent (MDA-MB-231) breast cancer cells. At high concentrations (up to 50 microM) the 17alpha-ethynylferrocenyl estradiol and 7alpha-ferrocenylmethylthio estradiol become cytotoxic (IC(50)=13.2 microM and 18.8 microM, respectively) while the 17alpha-ferrocenylestradiol remains non toxic. The low toxicity of these compounds support our hypothesis that electronic communication between the ferrocenyl and phenol moieties in the hydroxyferrocifens series is a key parameter in the generation of cytotoxic effects at submicromolar concentrations.
Experimental charge density analysis of three symmetrically substituted ferrocene derivatives: 1,1'- dimethyl ferrocene (1), decamethyl ferrocene (2), and 1,1'-diacetyl ferrocene (3) was conducted. The electron donating or accepting propensities of the ferrocene substituents were evaluated. The metal ligand interactions in all analyzed compounds were found to be similar in terms of charge density concentrations at Bond Critical Points (BCPs), laplacian values, and deformation density features. The monopole population of iron in all cases tend to be slightly negative, suggesting charge donation from Cp ligands. d orbital populations in all cases adopt values in agreement with theoretical calculations and ligand field theory. The charge distribution over analyzed molecules does not correlate with the formal oxidation potential in the analyzed compounds, as compound 2 in the currently studied structure takes the place suitable for an unsubstituted ferrocene. The non-intuitive low energy of the eclipsed conformation of 1 compound finds some explanation in the existence of a bond critical point between atoms of the two methyl groups in the structure. An asymmetry of the atomic surroundings of the two oxygen atoms in the 3 structure, reflected by the differences in charge rho(r(BCP)) and nabla(2)rho(r(BCP)) values and the shape of deformation density in the regions of oxygen lone electron pairs, is described.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.