Iron(II)-cyclopentadienyl compounds are cytotoxic against colon adenocarcinoma cell lines: Ethylenebis(diphenylphosphane) vs. triphenylphosphane.

Structure-activity studies aiming to understand the role of each coligand in the formulation of new metallodrugs is an important subject. In that frame, six new compounds with general formula [Fe(η5-C5H5)(dppe)(L)][CF3SO3] with L = benzonitriles (1-4) or carbon monoxide (5) and compound [Fe(η5-C5H5)(CO)(PPh3)2][CF3SO3] (6) were synthesized and compared with three other previously reported compounds [Fe(η5-C5H5)(CO)(L)(PPh3)][CF3SO3]. We were particularly interested in assessing the effect of dppe vs. (PPh3 + CO) for this set of compounds. For that, all compounds were tested against two human colon adenocarcinoma cell lines, Colo205 and the refractile Colo320 (expressing ABCB1, an efflux pump causing multidrug resistance), showing IC50 values in the micromolar range. The presence of dppe in the compound's coordination sphere over (PPh3 + CO) allows for more redox stable compounds showing higher cytotoxicity and selectivity, with improved cytotoxicity towards resistant cells that is not related to the inhibition of ABCB1. Further studies with GSH and H2O2 for selected compounds indicated that their antioxidant ability is not probably the main responsible for their cytotoxicity.