Coordination complexes of zinc and manganese based on pyridine-2,5-dicarboxylic acid N-oxide: DFT studies and antiproliferative activities consideration

We report here the design, synthesis, and antiproliferative activity of three coordination complexes [Mn-2(pydco)(2)(bpy)(2)(H2O)(2)]center dot 2H(2)O (1), [Zn(bpy)(Hpydco)(2)] (2), and [Zn(bpy)Cl(Hpydco)]center dot 2H(2)O (3) (H(2)pydco = pyridine-2,5-dicarboxylic acid N-oxide, bpy = 2,2'-bipyridine). Molecular structures of these complexes have been characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. According to the structural analysis, 1-3 are discrete complexes containing N- and O-donor ligands (bpy and pydco(2-)) in which pydco(2-) can be coordinated to the metal centres via the N-oxide oxygen and one carboxylate oxygen to generate a six-membered chelate ring. Also, these structures benefit from extensive intermolecular interactions such as hydrogen bonds and pi-interactions which are the major forces to make them more stable in the solid state. The energetic features of the pi-stacking interactions observed in compounds 1-3 have been computed and compared to the H-bonds. The interactions in the solid state have been also studied using the independent gradient model approach (IGM plot). The IGM-delta g approach uses a new descriptor (delta g) that locally represents the difference between a virtual upper limit of the electron density gradient and the true electron density gradient. This newly developed IGM methodology automatically extracts the signature of interactions between two given fragments. Finally, the antiproliferative properties of these complexes were tested on several cancer cell lines by MTT assay and flow cytometry. Also, to compare the antiproliferative activities of these complexes with common chemotherapy drugs, the antiproliferative property of cisplatin was evaluated as a reference and positive control.