Oxidative DNA cleavage promoted by polynuclear copper complexes bearing iminodiacetate chelator

The rigid-spaced polycopper(II) complexes of different benzyl polyiminodiacetic acid (IDA) ligands, Cu2L1 (complex 1, meta-dicopper complex), Cu2L2 (complex 2, para-dicopper complex) and Cu3L3 (complex 3) (H4L1, N,N,N′,N′-m-xylylenediamine tetraacetic acid; H4L2, N,N,N′,N′-p-xylylenediamine tetraacetic acid; H6L3, N,N,N′,N′,N″,N″-mesitylenetriamine hexaacetic acid) were prepared to explore the chelator’s role in determining the DNA cleavage behavior of polycopper complexes by comparing these complexes of IDA chelator with their analogues of bis(2-pyridylmethyl)amine (BPA) chelator. PolyCu(IDA) complexes 1–3 show the synergic effect between copper(II) centers. Their DNA cleavage activity follows an order of 3 > 1 > 2, which is consistent with their DNA binding abilities. However, this consistence was not observed in the case of polyCu(BPA) complexes according to our previous study. In addition, both the DNA binding ability and cleavage efficiency of polyCu(IDA) complexes are distinctly lower than those of polyCu(BPA) complexes. Furthermore, both the meta- and para-dicopper complexes are able to mediate linear DNA from supercoiled DNA at high complex concentration for polyCu(IDA) complexes, while for their analogues with BPA chelators, only the meta-dicopper analogue could induce the linear DNA from supercoiled DNA. These results suggested that the replacement of BPA chelator with the anionic IDA chelator alters distinctly the DNA cleavage behavior of rigid-spaced polycopper complexes.