Synthesis, Characterization, and DNA‐Binding and ‐Cleavage Properties of Dinuclear Cu II Salophen/Salen Complexes

Dinuclear Cu II complexes, [Cu 2 (salophen) 2 ] ( 1 ) and [Cu 2 (salen) 2 ] ( 2 ), with Schiff bases derived from salicylaldehyde and o ‐phenylenediamine (ophen) or ethylenediamine (en) were synthesized and characterized. They exhibit square‐planar geometry with CuN 2 O 2 coordination, where the dianionic Schiff base acts as a tetradentate N 2 O 2 donor ligand. Calf thymus (CT)‐DNA Binding studies revealed that the complexes possess good binding propensities ( K b =3.13×10 5 for 1 and K b =2.99×10 5   M −1 for 2 ). They show good DNA‐cleavage abilities under oxidative and hydrolytic conditions. Complex 1 binds and cleaves DNA more efficiently as compared to 2 due to the presence of an extended aromatic phenyl ring which might be involved in an additional stacking interaction with DNA bases. From the kinetic experiments, hydrolytic DNA‐cleavage rate constants were determined as 1.54 for 1 and 0.72 h −1 for 2 . The nuclease activities of 1 and 2 are significant, giving rise to (2.03–2.88)×10 7 ‐fold rate enhancement compared to non‐catalyzed DNA cleavage.