A two-dimensional copper(II) polymer with bridging μ-trans-oxamidate and μ2-picrate ligands: Synthesis, crystal structure and DNA binding studies

A two-dimensional copper(II) polymer with formula of [Cu2(dmapox)(pic)2]n · nCH3OH, where dmapox is the dianion of N,N′-bis[3-(dimethylamino)propyl]oxamide and pic is picrate, was synthesized and characterized by elemental analysis, conductivity measurement, IR and electronic spectra studies. The crystal structure of the complex has been determined by single-crystal X-ray diffraction. It crystallizes in monoclinic, space group P21/c with crystallographic data: a = 14.076(7) Å, b = 13.896(7) Å, c = 9.278(5) Å, β = 106.909(6)° and Z = 2. The structure consists of uncoordinated methanol molecules and two-dimensional copper(II) polymeric coordination network constructed by the bis-tridentate trans-dmapox and tridentate picrate ligands. The environment around the copper(II) atom can be described as a distorted octahedron and the Cu⋯Cu separations through μ-trans-oxamidate and μ2-picrate bridges are 5.227 Å and 8.359 Å, respectively. The copper(II) complex presents as a polymer in solid state, whereas in solution it presents as discrete neutral binuclear copper(II) species [Cu2(dmapox)(pic)2] due to the weak interactions between the copper(II) atoms and the para-nitro oxygens of the adjacent picrate ligands. The fluorescence titration and the ethidium bromide (EB) fluorescence displacement experiments reveal that the binding mode between the binuclear copper(II) complex [Cu2(dmapox)(pic)2] and Herring Sperm DNA might be intercalation.