The Fluorine Effect in Zwitterionic Half-Sandwich Iridium(III) Anticancer Complexes

The rational design by the introduction of fluorine into a compound has achieved success in the development of organic anticancer drugs. However, the fluorine effect in metal-based anticancer complexes has rarely been reported. In this contribution, we report the synthesis, characterization, chemical reactivity, and biological activity of a series of half-sandwich zwitterionic iridium(III) complexes containing different substituents in the η5-CpR ring. The molecular structures for complexes Ir1–Ir4 and Ir7 were determined by single-crystal X-ray crystallography techniques. Notably, the asymmetrically substituted fluoro complexes Ir4 and Ir6 in solution show two conformational isomers. These complexes have sufficient stability, exhibit fluorescence emission, and show potent catalytic activity in converting NADH to NAD+. The effect of the substituents in the η5-CpR ring for these zwitterionic complexes on their anticancer activity was systematically investigated. Surprisingly, the presence of fluorinated su...