Syntheses, crystal structures and anticancer activities of three novel transition metal complexes with Schiff base derived from 2-acetylpyridine and l-tryptophan

Three novel transition metal coordination complexes, Cu(C18H16N3O2)2·2CH3OH (1), Zn(C18H16N3O2)2·2CH3CH2OH (2) and Cd(C18H16N3O2)2·2CH3OH (3) (C18H16N3O2: 2-acetylpyridine-L-tryptophan) have been synthesized and characterized by IR, UV, elemental analysis, 1H NMR and X-ray diffraction single crystal analysis. The three crystals crystallize in the tetragonal crystal system, space group P43212. They are all six-coordinated by two nitrogen atoms from C=N, two nitrogen atoms from pyridine rings and two carboxylic oxygen atoms in different ligands, forming a distorted octahedron geometry. Each ligand serves as a bridging ligand to link metal ions through carboxylic oxygen atoms, leading to a three-dimensional coordination polymer. The anticancer activities of these three complexes on MDA-MB-231 breast cancer cells were also investigated. The results indicate that all of the three complexes can inhibit the cellular proliferation. Furthermore, Cd(C18H16N3O2)2·2CH3OH (3) has the highest anti-proliferative activity among the three complexes. In addition, Cd(C18H16N3O2)2·2CH3OH (3) can inhibit proteasomal chymotrypsin-like activity and also can induce apoptosis on human breast cancer MDA-MB-231 cells.