Structural topologies involving energetically significant antiparallel π-stacking and unconventional N(nitrile)⋯π(fumarate) contacts in dinuclear Zn(ii) and polymeric Mn(ii) compounds: antiproliferative evaluation and theoretical studies

Abstract

Two new poly-nuclear coordination compounds of Zn(II) and Mn(II) viz. [Zn₂(male)₂(3-AMpy)₄]·3H₂O (1) and [Mn(H₂O)₂(μ-fum)(3-CNpy)₂]_n (2) (male = maleate, fum = fumarate, 3-AMpy = 3-aminopyridine, 3-CNpy = 3-cyanopyridine) have been synthesized and characterized using single crystal X-ray analysis, elemental analysis, FT-IR spectroscopy, electronic spectroscopy and TGA. Compound 1 crystallizes as a maleato bridged Zn(II) di-nuclear complex, whereas compound 2 is a fumarato bridged coordination polymer of Mn(II). The lattice water molecules of compound 1 are aggregated via O–H⋯O hydrogen bonding interactions to form V-shaped (H₂O)₃ clusters which are enclathrated within the supramolecular layered assembly of the crystal structure. Unconventional N(nitrile)⋯π(fum) and antiparallel nitrile⋯nitrile contacts are involved in the stabilization of the 2D assembly of compound 2. The existence of such N(nitrile)⋯π(fum) interactions has been scarcely reported in the literature. Aromatic π-stacking combined with strong N–H⋯O H-bonding assemblies in 1 and unconventional N(nitrile)⋯π(fum) interactions in 2 have been further studied using DFT calculations and NCI plot computational tools. The energetic analysis of 2 indicates that the unconventional N(nitrile)⋯π(fum) interaction is energetically significant and a dominant force for the supramolecular assembly. Antiproliferative evaluation of the compounds reveals that the compounds induced significant cytotoxicity in Dalton's lymphoma (DL) cancer cell lines with nominal effects in normal healthy PBMC cells. The molecular docking study corroborates the results obtained in the apoptosis assays and established structure–activity relationships.