Synthesis, characterization, and cytotoxic activity studies of new N4O complexes derived from 2-({3-[2-morpholinoethylamino]-N3-([pyridine-2-yl]methyl) propylimino} methyl)phenol

A new unsymmetrical five‐coordinate Schiff base ligand (HL) with an N4O donor set (2) has been prepared by condensation of N1‐(2‐morpholinoethyl)‐N1‐([pyridine‐2‐yl]methyl)propane‐1,3‐diamine with 2‐hydroxy‐benzaldehyde. Metal complexes [ML]n+ (M = Zn2+, Cd2+, Mn2+, Cu2+, Ni2+, Ag+, Fe3+, and Co2+ (3–10) were synthesized by the reaction of the ligand and metal salts in ethanol. The resulting products were characterized by elemental analyses, infrared, 1H and 13C nuclear magnetic resonance spectra (in the case of Cd and Zn complexes), UV–Vis, electrospray ionization‐mass spectrometric, and conductivity measurements. The structure of the complexes [ZnL](ClO4) (3), [CdL](ClO4) (4), and [CuL](ClO4) (7) has been determined by single‐crystal X‐ray diffraction analysis. The metal complexes were determined to have a distorted trigonal bipyramidal (Zn and Cd) or a distorted square pyramidal (Cu) geometry. The cytotoxic potential of each compound (1–10) against MCF‐7 and MDA‐MB‐231 (breast cancer cells), PC‐3 (prostate cancer cells), and WI‐38 human normal lung fibroblast cells was evaluated using the MTT (3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyl tetrazolium bromide) assay. Compounds 1, 2, and 10 did not display any activity toward any cell line tested. None of the compounds except compound 8 was cytotoxic toward PC‐3. Compounds 4 and 8 showed the highest cytotoxic activity against the MCF‐7 and MDA‐MB‐231 cell lines. Because compounds 3, 6, and 9 have similar half‐maximal inhibitory concentration values against cancer cells and normal cells, these compounds displayed poor selectivity between cancer and normal cells. More importantly, it was observed that compound 5 acts differently toward different types of cell lines. For example, it displays lower cytotoxicity against the WI‐38 normal cell line than it does against the MDA‐MB‐231 cell line.