Synthesis, crystal structure and nuclease activity of a Schiff base copper(II) complex

A new Schiff base copper(II) complex, Cu(o-VANAHE)2 (o-VANAHE = 2-(o-vanillinamino)-1-hydroxyethane), has been synthesized and characterized. Single crystal X-ray diffraction results suggest that this complex structure belongs to triclinic crystal system, space group P1¯ with the following crystallographic parameters: a = 8.819(4) Å, b = 10.794(5) Å, c = 11.350(5) Å, α = 70.262(6)°, β = 70.816(6)°, γ = 78.360(6)°, V = 955.4(7) Å3, Z = 2, Dc = 1.571 Mg · m−3, and the final R1 = 0.0393, wR2 = 0.0994 for the observed reflections 2620(I > 2σ(I)). The molecular geometry is almost coplanar. Viscosity, fluorescence spectroscopy and cyclic voltammetry have been conducted to assess their interaction between this complex and DNA. Results showed that the copper(II) complex can increase DNA's relative viscosity and quench the fluorescence intensity of EB bound to DNA. The adding of DNA to the solution of Cu(o-VANAHE)2 causes a slight decrease in the voltammetric current, as well as a slight shift in the E1/2 to less negative potential. The interaction between the complex and DNA has also been investigated by submarine gel electrophoresis, interestingly, we found that the copper(II) complex can cleave circular plasmid pBR322 DNA to nicked and linear forms.