Unconventional enclathration of guest adipic acid and energetically significant antiparallel π-stacked ternary assemblies involving unusual regium-π(chelate) contacts in phenanthroline-based Ni(II) and Cu(II) compounds—Antiproliferative evaluation and theoretical studies

Abstract

Two Ni(II) and Cu(II) coordination compounds viz. [Ni(phen)3](0.5adp)(2NO3)·4.5H2O (1) and [Cu4(phen)4(H2O)2(OH)4]4NO3·2H2O (2) (where, phen = 1,10-phenanthroline and adp = adipic acid) have been isolated in aqueous medium and characterized by single crystal XRD, TGA, elemental analysis and spectroscopic techniques (FT-IR and electronic). Crystal structure analysis of compound 1 reveals the unconventional enclathration of adp moieties in the tetrameric supramolecular host cavities via O(adp)···π and C–H···π interactions. The formation of discrete [(NO3)4(H2O)10]4− cores in 1 and unusual enclathration of the nitrate water clusters in the supramolecular host cavity of 2 provide additional reinforcement to the layered assemblies. DFT calculations and NCI plot computational tools have been employed to investigate the energetically significant enclathrated adp moieties in supramolecular host cavities of 1 and the antiparallel π-stacked ternary assemblies involving regium-π(chelate) interaction in 2. To the best of our knowledge, this is the first report of enclathration of adipic acid, a long chain aliphatic dicarboxylic acid; and non-covalent regium-π bonding interaction involving chelate ring in metal organic compounds. Finally, the compounds have been screened for in vitro antiproliferative activities in Dalton's Lymphoma (DL) cancer cell lines considering cell cytotoxicity, apoptosis and molecular docking. The compounds exhibit considerable cytotoxicity in DL cells with nominal effects in healthy normal PBMC cells. The docking study reveals the effective binding affinity of the compounds with the active sites of BCL family antiapoptotic proteins.