Synthesis, characterization, interaction with DNA and cytotoxicity in vitro of novel pyridine complexes with Zn(II)

Four novel Zn(II) complexes [Zn(L1)(bipy)(H2O)2]·4H2O(1), [Zn(L1)(phen)(H2O)2]·4H2O(2), [Zn(L2)(bipy)(H2O)2]·4H2O(3) and [Zn(L2)(phen)(H2O)2]·4H2O (4), where bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline, L1 = 2,2′-bipyridine 5,5′-dicarboxylic acid, L2 = 2,2′-bipyridine-4,4′-dicarboxylic acid, have been synthesized and characterized using IR, 1H NMR, element analysis and single-crystal X-ray diffractometry. The unit cell parameters for the title complex (1), a = 7.9621(10) Å, b = 12.6853(17) Å, c = 13.3714(17) Å, α = 68.549(2)°, β = 79.065(2)°, γ = 88.723(2)°, V = 1232.5(3) Å3, Z = 15, space group,P-1(2).complex (4) a = 9.5710(5) Å, b = 14.1140(7) Å, c = 19.0045(9) Å, α = 90°, β = 99.9920(10)°, γ = 90°, V = 2528.3(2) Å3, Z = 32, space group, P121/n 1(14). The binding of the complexes with fish sperm DNA (FS-DNA) was investigated by electronic absorption spectra and fluorescence spectroscopy, showing that the complexes have the ability of interaction with DNA of intercalative mode. The intrinsic binding constant K of the complexes with FS-DNA is 0.37 × 105 M−1 (1) 0.73 × 105 M−1 (2), 0.98 × 105 M−1 (3), and 1.05 × 105 M−1 (4). The results indicate that the four complexes bound to DNA with different binding affinity, in the order complex 4 > 3 > 2 > 1. Gel electrophoresis assay demonstrates the ability of the complexes to cleave the pBR322 plasmid DNA. The cytotoxic activity of the complexes was tested against four different cancer cell lines. The four complexes exhibited cytotoxic specificity and significant cancer cell inhibitory rate.

Graphical abstractIn the complex, Zn(II) is six coordinated by four nitrogen atoms from bipy and 2,2′-bipyridine-5,5′-dicarboxylic acid ligand and two oxygen atoms from H2O, with the axial Zn–N(1) distance (2.204 Å) and Zn–N(3) distance (2.161 Å) elongated in comparison to Zn–N(2) distance(2.171 Å) and Zn–N(4) distance (2.179 Å).Figure optionsDownload full-size imageDownload as PowerPoint slide