Synthesis and characterization of bis(azine) ligands and metal complexes: DNA-interaction and extraction properties for metals and dichromate anions

Abstract

Two new bis(bidentate) azine ligands were prepared by linking (1Z,1'Z)-1,1'-{butane-1,4-diylbis[oxyben-zene-4,1- diyl(1Z)eth-1-yl-1-ylidene]}dihydrazine to salicylaldehyde and pyridine-2-carbaldehyde, 1,4-bis{4-{(1E)-1-((2E)-(2- hydroxybenzene--2-ylmethy-lidene)hydrazonylidene)ethyl}phenoxy}butane (H_2L^1), and 1,4-bis{4-{(1E)-1-((2E)-(pyridine--2-ylmethylidene) hydrazonylidene)ethyl}phenoxy}butane (L^2), respecti- vely. Two kinds of copper(II) and nickel(II) complexes with different ligands were prepared. Reaction of H_2L^1 with Cu(II) and Ni(II) acetate with 1:1 molar ratio gave double stranded binuclear bis(azine) complexes with stoichiometry [M(L^1)]_2 containing {M^{II}N_2O_2} centers. On the other hand, 1:1 molar ratio reaction of Cu(II) and Ni(II) chloride with L^2 yielded mononuclear metal complexes with general stoichiometry [M(L^2)Cl_2] containing {M^{II}N_2N_2} centers. The structures of both bis(azine) ligands and complexes were identified by elemental analysis, infrared spectra, UV--Vis electronic absorption spectra, magnetic susceptibility measurements, and TGA. DNA binding and DNA cleavage activities of the mononuclear complexes of L^2, [M(L^2)Cl_2] were examined by using UV-Vis titration and agarose gel electrophoresis, respectively. The results indicate that mononuclear complexes, especially [Cu(L_2)Cl_2], bind significantly calf thymus DNA and cleaves pBR322 DNA. Furthermore, the complexing properties of the bis-azine ligands toward selected transition metal cations and dichromate anions were also reported. It was found that bis(azine) ligands have high extraction ability towards dichromate anions.