Effect of coordination sphere of the copper center and Cu―Cu distance on catechol oxidase and nuclease activities of the copper complexes

Abstract

To explore the effect of Cu―Cu distance in the structure of copper complexes on their catechol oxidase and nuclease activity, six copper complexes with a similar coordination sphere but different Cu―Cu distances were synthesized and characterized with elemental analysis, single‐crystal X‐ray diffraction, molar conductivity measurements, IR and UV–visible spectroscopy. Complex 1 is a binuclear copper complex and complex 4 is a polynuclear complex with a Z‐chain structure, as evidenced by their crystal structures. Complementary characterizations showed that complexes 2 and 3 have a similar binuclear structure to the complex 1; and complexes 5 and 6 are analogous to complex 4. The catechol oxidase activity of complexes 1, 2, 3 is quite akin to that of 4, 5, 6, suggesting that the catechol oxidase activity of the complexes was determined by the coordination environment of the copper center, when Cu―Cu distance is large. In contrast, DNA cleavage activity of the complexes 1, 2 and 3 are much higher than that of 4, 5 and 6, indicating that the planar ligand structure in the complexes 4, 5 and 6 is more critical than the copper coordination sphere and the Cu―Cu distance for their nuclease activity. Copyright © 2014 John Wiley & Sons, Ltd.