Photoinduced and Self‐Activated Nuclease Activity of Copper(II) Complexes with N‐(Quinolin‐8‐yl)quinolin‐8‐sulfonamide – DNA and Bovine Serum Albumin Binding

Two CuII complexes with a new quinoline sulfonamide derivative and phenanthroline (phen), [Cu(QSQ)(phen)]ClO4·0.5H2O (1) and [Cu(QSQ)(phen)(H2O)]ClO4 (2) [HQSQ = N‐(quinolin‐8‐yl)quinolin‐8‐sulfonamide], have been synthesized and physicochemically characterized. Single‐crystal X‐ray diffraction studies have revealed a highly distorted trigonal‐bipyramidal structure for 1 (τ = 0.68) and an almost perfect trigonal‐bipyramidal geometry for 2 (τ = 0.92). DNA binding studies, which were performed by thermal denaturation, viscometry, fluorescence spectroscopy, and cyclic voltammetry, indicated a partial intercalation of 1 with Kapp = 2.45 × 106 M–1. The nuclease activity of 1 was investigated upon photoirradiation, with ascorbate/H2O2 as the activating agent, and also in the absence of any external reagent. In all cases, 1 was able to perform DNA cleavage, and its nuclease efficiency varied in the order ascorbate/H2O2 > photoirradiation > without external cofactors. Mechanistic investigations suggest an oxidative cleavage of DNA involving reactive oxygen species (ROS). The protein binding ability of 1 was also studied with bovine serum albumin (BSA) as a model protein.