Terephthalato and succinato bridged Mn(II) and Zn(II) coordination polymers involving structure-guiding H-bonded tetrameric assemblies: Antiproliferative evaluation and theoretical studies

Abstract

Two new coordination polymers of Mn(II) and Zn(II) viz. {[Mn(µ-tp)(3-Ampy)2(H2O)2]2(3-Ampy)·2(H2O)}n (1) and {[Zn(µ-succ)(3-Ampy)2]·2H2O}n (2) (tp = terephthalate, 3-Ampy = 3-aminopyridine, succ = succinate) have been synthesized and characterized using elemental and spectroscopic analyses, TGA and single crystal X-ray diffraction techniques. Uncoordinated 3-AMpy and water molecules of the polymeric co-crystal hydrate 1 are involved in the formation of cyclic tetrameric {(3-Ampy)2(H2O)2} assembly which provide rigidity to the structure. The presence of guest 3-Ampy and water molecules in the voids of supramolecular Mn(II) host tetramer in 1 provides additional reinforcement to the crystal structure. The lattice water molecules of 2 are aggregated via non-covalent interactions to form discrete cyclic {(H2O)4} tetrameric clusters in the crystal structure. Density functional theory (DFT), non-covalent index (NCI) plot and quantum theory of atoms in molecules (QTAIM) computational analyses reveal that the supramolecular H-bonded cyclic tetrameric structure-guiding synthon in 1 and the (H2O)4 cyclic water clusters in 2 have significant energetic contribution towards the stability of the polymers. In vitro anticancer activities of the compounds considering trypan blue and apoptosis assays revealed that the compounds induce concentration dependent cytotoxicity in Dalton’s lymphoma (DL) cancer cells with nominal effects in normal peripheral blood mononuclear cells (PBMC) cells. Comparative analysis reveals that compound 2 induced higher apoptosis in DL cells; which is well consistent with the trypan blue exclusion assay. Molecular docking and pharmacophore modelling studies of the compounds reveal that the compound 2 significantly interacts with the antiapoptotic proteins to establish structure activity relationship (SAR).