Synthesis, characterization, and DNA-binding of enantiomers of iron(II) Schiff base complexes

Two pairs of iron(II) chiral enantiomers fac-Δ-[Fe(S-L1)3][ClO4]2 and fac-Λ-[Fe(R-L1)3][ClO4]2 (Δ-1 and Λ-1), fac-Δ-[Fe(S-L2)3][ClO4]2 and fac-Λ-[Fe(R-L2)3][ClO4]2 (Δ-2 and Λ-2), L1 = (R/S)-(±)-1-naphthyl-N-(pyridine-2-ylmethylene)ethanamine, L2 = (R/S)-(±)-2-naphthyl-N-(pyridine-2-ylmethylene)ethanamine were synthesized and characterized by elemental analysis, IR, UV–Vis, CD and 1H NMR spectra. The X-ray structural analyses of Λ-1 and Δ-2 revealed that the iron(II) complexes possess octahedral coordination geometry for N6 donor atoms by three bidentate ligands. R-L1 ligand induces the fac-Λ isomer, while S-L2 ligand induces the fac-Δ isomer. The enantioselective binding of iron(II) chiral enantiomers to calf-thymus DNA (ct-DNA) has been investigated by methods of UV–Vis, fluorescence, and circular dichroism spectrometry. All the complexes could bind to ct-DNA and showed different binding affinities with the binding constants ranging from 0.91 × 105 to 1.43 × 105 M−1. Moreover, the Δ enantiomers exhibited more efficient DNA interaction with respect to the Λ enantiomers.

Two pairs of iron(II) chiral enantiomers fac-Δ-[Fe(S-L1)3][ClO4]2 and fac-Λ-[Fe(R-L1)3][ClO4]2 (Δ-1 and Λ-1), fac-Δ-[Fe(S-L2)3][ClO4]2 and fac-Λ-[Fe(R-L2)3][ClO4]2 (Δ-2 and Λ-2), were synthesized and characterized. The X-ray structural analyses of Λ-1 and Δ-2 revealed that the iron(II) complexes possess octahedral coordination geometry for N6 donor atoms by three bidentate ligands. R-L1 ligand induces the fac-Λ isomer, while S-L2 ligand induces the fac-Δ isomer. The enantioselective binding constants of iron(II) chiral enantiomers to calf-thymus DNA (ct-DNA) range from 0.91 × 105 to 1.43 × 105 M−1. Moreover, the Δ enantiomers exhibited more efficient DNA interaction with respect to the Λ enantiomers.Figure optionsDownload as PowerPoint slide