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 Cu-II complexes with a new quinoline sulfonamide derivative and phenanthroline (phen), [Cu(QSQ)(phen)]ClO(4)0.5H(2)O (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 ( = 0.68) and an almost perfect trigonal-bipyramidal geometry for 2 ( = 0.92). DNA binding studies, which were performed by thermal denaturation, viscometry, fluorescence spectroscopy, and cyclic voltammetry, indicated a partial intercalation of 1 with K-app = 2.45x10(6) 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.