A new two-dimensional polymeric copper(II) complex bridged both by oxamidate and azide groups: synthesis,structure and DNA binding properties

A new two-dimensional polymeric copper(II) complex, Cu₂(heae)(N₃)₂] _n , where heae stands for the dianion of N,N′-bis(N-hydroxyethylaminoethyl)oxamide, has been synthesized and characterized by elemental analysis, molar conductivity measurement, IR, electronic spectral studies and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic system, P2₁/c space group with crystallographic data: a = 9.1588(18) Å, b = 6.6238(13) Å, c = 14.602(3) Å and Z = 2. The X-ray analysis reveals a two-dimensional copper(II) polymeric coordination network constructed by bis-tridentate chelated Cu(trans-heae)Cu]²⁺ building blocks and end-on azido ligands. The environment around the copper(II) atom can be described as a square-based pyramid. The azido bridge is very asymmetric with one Cu–N bond distance short and the other long. The Cu ··· Cu separations through μ-trans-oxamidate and μ-azido bridges are 5.2996(13) Å and 4.2464(7) Å, respectively. The copper(II) complex is a polymer in the solid state, whereas in solution it exists as discrete neutral binuclear copper(II) species. Coordination mode of the azide in solution is proved by electronic spectra. The DNA-binding properties of the binuclear copper(II) species were investigated by emission spectral and electrochemical techniques, indicating the binuclear copper(II) complex binds to HS-DNA via a groove mode.