Redox behavior and biological properties of ferrocene bearing porphyrins

In order to improve antimicrobial effects of previously studied meso-tetrakis(4-ferrocenylphenyl)porphyrin 1, we have modified its structure by replacing two trans-positioned ferrocenylphenyl moieties with methoxy methylene substituted tert-butylphenyl moieties. Newly synthesized 5⁴,15⁴-bis-(ferrocenyl)-10⁴,20⁴-bis-(tert-butyl)-10²,10⁶,20²,20⁶-tetrakis-(methoxy-methylene)-5,10,15,20-tetraphenylporphyrin 4 was chemically characterized in detail (by NMR, UV/Vis, IR, MALDI-TOF and ESI MS spectrometry, cyclic voltammetry, prediction of the relative lipophilicity as well as computational methods) and its biological effects were studied in terms of its antibacterial and antifungal activity (both with and without photoactivation), cytotoxicity, hemolysis and DNA cleavage. New ferrocene bearing porphyrin 4 has demonstrated a broader antimicrobial spectrum and modified effects on eukaryotic cells compared to 1. This was discussed in terms of its i) increased lipophilicity, while exhibiting lower toxicity, and ii) the redox potential of a two-electron process that is shifted to lower values, in comparison to ferrocene, thus, entering the physiologically available range and being activated towards redox interactions with biomolecules.