Iron(III) Catecholates for Cellular Imaging and Photocytotoxicity in Red Light

Abstract

Iron(III) complexes [Fe(L)(L′)(NO3)]—in which L is phenyl-N,N-bis[(pyridin-2-yl)methyl]methanamine (1), (anthracen-9-yl)-N,N-bis[(pyridin-2-yl)methyl]methanamine (2), (pyreny-1-yl)-N,N-bis[(pyridin-2-yl)methyl]methanamine (3–5), and L′ is catecholate (1–3), 4-tert-butyl catecholate (4), and 4-(2-aminoethyl)-benzene-1,2-diolate (5)—were synthesized and their photocytotoxic properties examined. The five electron-paramagnetic complexes displayed a FeIII/FeII redox couple near −0.4 V versus a saturated calomel electrode (SCE) in DMF/0.1 m tetrabutylammonium perchlorate (TBAP). They showed unprecedented photocytotoxicity in red light (600–720 nm) to give IC50≈15 μM in various cell lines by means of apoptosis to generate reactive oxygen species. They were ingested in the nucleus of HeLa and HaCaT cells in 4 h, thereby interacting favorably with calf thymus (ct)-DNA and photocleaving pUC19 DNA in red light of 785 nm to form hydroxyl radicals.