Towards polynuclear metal complexes with enhanced bioactivities: Synthesis, crystal structures and DNA cleaving activities of CuII, NiII, ZnII, CoII and MnII complexes derived from 4-carboxy-1-(4-carboxybenzyl) pyridinium bromide

► 4-Carboxy-1-(4-carboxybenzyl)pyridinium bromide (H2CcbpBr) and its five metal complexes were synthesized and fully characterized. ► Complexes 1, 2 and 3-5 formed a polynuclear structure, an ionic metal complex and mononuclear structures, respectively. ► Complex 1 was capable of efficiently cleaving DNA, most probably via an oxidative mechanism. ► Complex 1 exhibited the maximal catalytic rate constant kmax of 0.50 h−1 and Michaelis constant KM of 0.60 mM, respectively. ► The high cleaving efficacy of complex 1 is thought to be due to its polynuclear structure.