Novel tetranuclear distorted open-cubane copper complex containing oximate bridges: Synthesis, crystal structure, DNA binding and cleavage activity

The synthesis, molecular structure, DNA binding and nuclease activity of Cu4O4 open-cubane tetranuclear copper(II) complex with 3-[2-[(ethyl amino)ethyl]imino]-2-butanoneoxime (HL) are reported for the first time. The neutral tetranuclear [Cu4L4(ClO4)4] complex crystallizes in tetragonal space group P4¯21c with the unit cell parameters; a = 13.798(4) Å, b = 13.798(4) Å, c = 14.119(6) Å, V = 2688(16) Å3, Z = 8, R = 0.0636. Symmetrically equivalent copper atoms exhibit a CuN3O3 elongated distorted octahedral coordination environment, with three nitrogen atoms of the L− ligand and one oxime-oxygen atom of second L− ligand at equatorial positions, one oxime-oxygen atom of the third L− ligand and perchlorate oxygen at axial positions. The complex shows quasireversible cyclic voltammetric response at 0.805 V (ΔEp = 277 mV) at 100 mV s−1 in DMF for the Cu(II)/Cu(I) redox couple. The binding study of the complex with calf-thymus DNA has been investigated using absorption spectrophotometry. The complex shows strong nuclease activity on stranded pBR 322 plasmid DNA in the presence of hydrogen peroxide and marginal nuclease activity in the presence of reducing agent (dithiothreitol).

The reaction of 3-[2-[(ethyl amino)ethyl]imino]-2-butanoneoxime (HL) with Cu(ClO4)2·6H2O in the presence of Et3N, leads to the formation of tetranuclear distorted open-cubane Cu4O4 complex. The resulting neutral [Cu4L4(ClO4)4] complex is the first example of distorted Cu4O4 open-cubane containing oximate bridges.Figure optionsDownload as PowerPoint slideHighlights
► Synthesized a novel tetranuclear copper(II) complex having oximate bridges.
► The complex has distorted open-cubane Cu4O4 core.
► The central core of the complex has two types of chelate rings.
► The complex acts as DNA groove binder.
► The complex cleaves DNA quite efficiently by oxidative mechanism.