Antiproliferative evaluation and supramolecular association in Mn(II) and Zn(II) bipyridine complexes: Combined experimental and theoretical studies

Two new coordination complexes viz. [Mn-2(mu-O,O'-4-Mebz)(2)(bpy)(2)(mu(2)-H2O)(4-Mebz)(2)] (1) and [Zn(bpy)(pdc)(H2O)]center dot 3.5H(2)O (2) (where bpy = 2,2'-bipyridine, 4-Mebz = 4-methyl benzoate and pdc = 2,6-pyridine dicarboxylate) were synthesized and structurally characterized by single crystal X-ray diffraction, FT-IR, electronic spectroscopy, Thermogravimetric Analysis (TGA) and Powder X-ray diffraction (PXRD) techniques. Complex 1 consists of a dinuclear Mn(II) unit bridged by a solvent water molecule while 2 is a mononuclear complex. The supramolecular assemblies found in the solid state of both complexes have been described. In 2, several pi-stacking interactions modes have been further studied using Density Functional Theory (DFT) calculations. Furthermore, the activity of the complexes against a few pathogenic bacteria has been studied and confirmed. Finally, the antiproliferative activities of both complexes have been studied in T-cell lymphoma cell line by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, apoptosis assay and molecular docking simulation. Both the complexes exhibit gratifying cytotoxicity through apoptotic cell death with negligible cytotoxicity (similar to 5-10%) in normal cells. It is worth mentioning that Mn(II) and Zn(II) complexes exhibit interaction modes with highly expressed cancer target proteins under study with higher binding affinity and the results are comparable with reference inhibitors.