Syntheses, structures, DNA-binding, cytotoxicity and apoptosis of manganese(II) and ferrous(II) complexes containing 4-sulfobenzoate anion with N,N-heterocyclic amines

Three new complexes, {[Mn(2,2′-bipy)(4,4′-bipy)0.5(4-sb)(H2O)](H2O)2}n (1), [Mn(phen)2(4-sb)(H2O)](4,4′-bipy)0.5(H2O)3 (2), and [Fe2(phen)6](4-Hsb)(H2O)5 (3) [4-sb = 4-sulfobenzoate dianion, 2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine, phen = 1,10-phenanthroline], have been synthesized and structurally characterized. The interaction of complex with HS-DNA was investigated by carrying out UV−vis absorption spectrum and fluorescence ethidium bromide displacement experiment. The DNA-binding constants Kb of complexes 1, 2, and 3 were calculated to be 7.39 × 105 M−1, 3.94 × 105 M−1, and 9.34 × 105 M−1, respectively. The results indicated that these complexes interact with HS-DNA through intercalative mode. Competitive studies with ethidium bromide (EB) further showed that the complexes bind to DNA probably via intercalation. The complexes were tested for antiproliferative activities on a panel of cell lines (MCF-7, HepG-2, A549, BGC823, and HTR-8) by MTT method, three complexes can inhibit the tumor cell proliferation, but complex 1 is less cytotoxic than other two complexes. The apoptosis assay was assessed with the Annexin-V/PI double staining methods and the results revealed that complexes induced the HepG-2 cells apoptosis.