Synthesis, Crystal Structure and DNA Binding Studies of a New Binuclear Cobalt(III) Complex Bridged Both by μ-Peroxo and μ-Hydroxyl Groups

A new binuclear cobalt(III) complex bridged both by mu-peroxo and mu-hydroxyl groups, and end-capped with 4,4'-dimethyl-2,2'-bipyridine (Me(2)bpy), namely, [CO2(mu-O-2)(mu-OH)(Me(2)bpy)(4)](ClO4)(3), has been synthesized and characterized by elemental analysis, IR, UV and single-crystal X-ray diffraction. It crystallizes in the monoclinic system, space group P2(1)/c and Z=4, with a=24.148(5)angstrom, b=10.628(2)angstrom, c=16.306(3)angstrom, and beta=90.74(3)degrees. The single crystal X-ray analysis reveals that the complex is composed of three perchlorate anions and a binuclear cobalt(III) cation, in which the cobalt(III) atoms are bridged both by hydroxyl and peroxo groups. Each cobalt(III) atom exhibits an octahedral geometry. A three-dimensional supramolecular arrangement in the crystal is generated by non-classical hydrogen bonds. The DNA-binding properties of the complex were explored by using absorption and emission spectra and electrochemical methods. The result suggests that the binuclear cobalt(III) complex interacts with herring sperm DNA (HS-DNA) in the mode of intercalation with the intrinsic binding constant of 1.1x10(3) M-1.