The Single- and Double-Strand Cleavage of DNA by a Cationic Dicobalt Complex by Visible Light

Abstract

Abstract A one-pot synthesis of a new polycationic organo–dicobalt complex having dual cationic alkyl groups as radical sources is reported. The complex was characterized by elemental analysis, UV–vis, 1H NMR, IR, and CSI-mass spectroscopies. CSI-MS afforded intact parent ion peak with labile cobalt–carbon bonds in the complex. The complex was photosensitive, and photocleavage of the cobalt–carbon bonds upon irradiation with visible light produced dual cationic carbon-centered radicals that were detected by EPR spin-trapping. Strong binding of the dicobalt complex with six cationic moieties toward DNA was confirmed by ethidium bromide displacement assays with Kapp = 3.2 × 107 M−1 at 298 K, the value was 100 times that of corresponding monocobalt complex with Kapp = 3.3 × 105 M−1. The dicobalt complex exhibited high ability for single- and double-strand DNA cleavage in comparison with that for the corresponding monocobalt complex under irradiation with visible light.