Synthesis, crystal structures, DNA binding and cleavage properties and protein binding activities of three mononuclear cobalt(II) complexes

Abstract

Three new mononuclear cobalt(II) complexes containing ligands with extended planar quinoxaline moieties, {dipyrido[3,2-a:2′,3′-c]phenazine (dppz) or dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq)}, viz. [Co(dppz)(acac)2] · CH3OH (1), [Co(dpq)(tfnb) 2] (2) and [Co(dpq)(dbm)2] (3), where acac = acetylacetonate, tfnb = benzoyltrifluoroacetone and dbm = dibenzoylmethane, have been synthesized and structurally characterized as octahedral complexes. The binding ability of the complexes with calf thymus (CT)-DNA has been investigated by spectroscopic and viscosity measurements. Results indicate that all complexes bind to CT-DNA via intercalative mode, and the DNA binding affinity of dppz complex 1 is apparently stronger than that of dpq complexes 2 and 3. Furthermore, DNA photocleavage experiments indicate that these complexes are efficient DNA cleaving agents in UV-A (365 nm) and hydroxyl radical (HO ·), singlet oxygen (1O2) and superoxide anion (1O2-) serve as the major cleavage active species. In addition, interaction of the complexes with bovine serum albumin (BSA) was investigated using UV - visible and fluorescence methods, which indicated that all complexes could quench the intrinsic fluorescence of BSA in a static quenching process. Copyright © 2014 John Wiley & Sons, Ltd.