Mononuclear copper(II) and binuclear cobalt(II) complexes with halides and tetradentate nitrogen coordinate ligand: Synthesis, structures and bioactivities

Abstract

In this work, we present the synthesis of four mononuclear copper(II) complexes [Cu(bdpab)X]Y and two binuclear cobalt(II) complexes [Co(bdpab)Cl]2Y2 (X=Cl−, Br−; Y=PF6−, BF4−) with tripodal N4-coordinate N-benzyl-N′,N′-bis(3,5-dimethyl-1H- pyrazol-1-yl)-2-methy]-1,2-ethylenediamine (bdpab) and the complexes were characterized by elemental analyses, IR spectral data, molar conductivity measurement, EPR and crystal structure determination. Single crystal X-ray diffraction studies indicate that the copper centers in the complexes [Cu(bdpab)Cl]PF6 and [Cu(bdpab)Br]PF6 have distorted square pyramidal geometry and complex [Co(bdpab)Cl]2(PF6)2 has octahedral geometry and two [Co(bdpab)Cl]+ units are linked by two (µ-Cl) bridges. Copper(II) complexes form 1D supramolecular chain along c-axis through C-H-π interaction whereas cobalt(II) complex form 1D supramolecular chain along a-axis through π-π interaction. The antimicrobial activity of complexes [Cu(bdpab)Cl]PF6, [Cu(bdpab)Br]PF6 and [Co(bdpab)Cl]2(PF6)2 were investigated against gram positive (Bacillus subtilus, Streptococcus aureus) and gram negative (Escherichia coli, Pseudomonas aeruginosa) bacterial strains by agar well dilution method and have demonstrated significant antimicrobial activity of the compounds. [Co(bdpab)Cl]2(PF6)2 exhibited the best antibacterial activity among all the synthesized complexes. The studies on the interaction of complexes and DNA by agarose gel electrophoresis method revealed that the complexes can effectively cleave the circular plasmid DNA at very low concentrations. The cytotoxic activity of the complexes against A549 lung cancer cells showed that the complexes have better cytotoxic activity than corresponding metal salts and [Cu(bdpab)Br]PF6 complex has best cytotoxic activity among the synthesized complexes.