Structure, speciation, DNA binding and nuclease activity of two bipyridyl-zinc complexes bearing trimethylaminomethyl groups

The Zn(II) complexes of two bipyridyl derivatives with trimethylaminomethyl groups, [Zn(L1)3](ZnBr4)(ClO4)2Br4 · 12H2O (1) and [Zn(L2)3](ClO4)8 · H2O (2) (L1 = [4,4′-(Me3NCH2)2-bpy]2+, L2 = [5,5′-(Me3NCH2)2-bpy]2+ and bpy = 2,2′-bipyridyl), were synthesized and characterized. The structure of complex 1 has been determined by X-ray diffraction, and the configuration of ligand-coordinated Zn(II) ion can be well described as distorted octahedral. Species distribution of both complexes in aqueous solution was investigated by potentiometeric titration. DNA-binding ability of both complexes was studied by UV spectroscopy titration. Under hydrolytic condition, both complexes (150 μM) can effectively cleave plasmid pBR322 DNA from supercoiled to nicked form, giving hydrolysis rate constants of 2.63 × 10−5 and 9.92 × 10−5 s−1, respectively (pH 7.75, 37 °C). The result shows that complex 2 is one of the most active artificial nucleases based on zinc.