Coordination polymer of zinc based on chiral non-racemic trans-N,N′-bis-(2-hydroxy-1-naphthalidehydene)-(1R,2R)-cyclohexa-nediamine: Synthesis, crystal structure, novel coordinational models and anticancer activity

Chiral Schiff base trans-N,N′-bis-(2-hydroxy-1-naphthalidehydene)-(1R,2R)-cyclohexanediamine C28H26N2O2 (H2L) and its chiral coordination polymer [Zn(H2L)Cl2]n were prepared and characterized by infrared spectroscopy, elemental analyses and single-crystal X-ray diffraction analysis. X-ray crystallography showed that the proton transfer of phenolic hydroxyl occurred in the chiral ligand and the complex. The chiral ligand demonstrates a one-dimensional helix chain. The Zn(II) ion is four-coordinated by two oxygen atoms in different ligands and two chlorine ions, forming a distorted tetrahedron geometry. The two coordinated oxygen atoms exist in different forms, one is in keto form and the other in phenol form. The metal ions are bridged by chiral ligands and construct supramolecular which displays a one-dimensional dextrorotatory helix chain. The anticancer activities of H2L and its chiral coordination polymer [Zn(H2L)Cl2]n on MDA-MB-231 breast cancer cells were also investigated. The results indicate that both of H2L and [Zn(H2L)Cl2]n can inhibit the cellular proliferation. Furthermore, [Zn(H2L)Cl2]n has higher antiproliferative activity than that of H2L. In addition, [Zn(H2L)Cl2]n can inhibit proteasomal chymotrypsin-like activity and also can induce apoptosis on human breast cancer MDA-MB-231 cells.