Mn(II) complexes with sulfonamides as ligands.: DNA interaction studies and nuclease activity

Sulfonamides derived from 8-aminoquinoline react with Mn(II) and Mn(III) salts to form Mn(II) complexes; the Mn(III) species are reduced to the divalent state in the presence of 1,10 phenanthroline and bipyridine. Their molecular structure, determined by single crystal X‐ray diffraction, show that all the complexes present a distorted octahedral geometry, in which the deprotonated sulfonamide acts as a bidentate ligand. UV–visible spectroscopy and changes in the melting temperature (Tm) of calf thymus DNA show a strong interaction of these complexes with DNA. The significant hypochromicity of the charge transfer transition at 370 nm without an appreciable change in wavelength and the minor changes in the relative viscosity of calf thymus DNA have been attributed to an interaction between the surface of DNA and the complexes. [Mn(qbsa)2(MeOH)2], [Mn(qbsa)2(phen)], [Mn(qtsa)2(H2O)2] and [Mn(qtsa)2(phen)] (where qbsa = N-quinolin-8-yl-bencenesulfonamide, qtsa = N-quinolin-8-yl-p-toluenesulfonamide and qnsa = N-quinolin-8-yl-naftalenesulfonamide) exhibit a prominent nuclease activity and the mechanism of DNA cleavage is investigated.

Graphical abstractMn(II) forms distorted octahedral compounds with sulfonamides derived from 8-aminoquinoline. DNA binding studies suggest that the compounds interact at the surface of DNA. Ternary Mn(II) complexes with phenanthroline behave as very efficient chemical nucleases.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Mn(II) complexes with sulfonamides derived from 8-aminoquinoline were synthesized. ► The compounds were characterized by means of X-ray diffraction. ► Their interaction with DNA was studied by different techniques. ► This study indicated an interaction between the surface of DNA and the complexes. ► The Mn(II)-sulfonamide complexes exhibit a prominent nuclease activity.