New insights on the application of half‐sandwich complexes with metal–iodide bonds for agricultural fungicides

Cyclopentadienyl half-sandwich complexes of cobalt and iron with metal–iodide bonds were reported to efficiently inhibit the growth of phytopathogenic fungi. With the aim of investigating the structure/activity relationships, further in vitro experiments were carried out. Cyclic voltammetric characterization, chemical stability, and antiradical activity were performed in two solvents: dimethyl sulfoxide and acetone. The iodide ion removal from the complex appears to be the key point of antifungal activity. Moreover, a preliminary cell viability test on human keratinocytes was also assessed in order to verify the nontoxic effect of tested compounds. The cytotoxicity for all the complexes was comparable with that shown by povidone iodide, a common antifungal agent recognized as safe (IC50 > 300 mM). Furthermore, the work proposes an additional roadmap (sequence of experiments) at the initial antifungal activity tests, which improves insight into their mechanism of action.