Unconventional π-hole and Semi-coordination regium bonding interactions directed supramolecular assemblies in pyridinedicarboxylato bridged polymeric Cu(II) Compounds: Antiproliferative evaluation and theoretical studies

Two pyridinedicarboxylato bridged 1D coordination polymers of copper(II) viz.; {[Cu(2,5-PDC)(Hdmpz)2]& sdot;H2O}n (1) and {[Cu(2,3-PDC)]& sdot;10H2O}n (2) (where, Hdmpz = 3,5-dimethyl pyrazole, PDC = pyridinedicarboxylate) have been isolated and characterized using TGA, elemental analysis, spectroscopic (IR, electronic) and single crystal X-ray diffraction techniques. Crystal structure analysis of the compounds 1 and 2 reveals that unconventional C-HMIDLINE HORIZONTAL ELLIPSIS pi(carbonyl) and intramolecular OMIDLINE HORIZONTAL ELLIPSISC pi-hole interactions provide stability to the crystal structures, respectively. Such C-HMIDLINE HORIZONTAL ELLIPSIS pi(carbonyl) and intramolecular OMIDLINE HORIZONTAL ELLIPSISC pi-hole interactions are scarcely reported in the literature. Theoretical calculations have been performed to analyze the unconventional non-covalent interactions observed in the solid-state structures of 1 and 2 using NCI plot and QTAIM computational tools. We have also theoretically explored the semi-coordination (regium) Cu-Oaxial bonds present in the compound 2. The polymers have been further investigated for potential antiproliferative activities considering cell viability and apoptosis assays against Dalton's lymphoma (DL) cancer cell lines and the results were compared with cisplatin (reference drug) in the same experimental conditions. The compounds significantly induce cytotoxicity in DL cells with nominal cytotoxicity in normal PBMC cells. The molecular doking simulation performed with the antiapoprotic protiens reveals strong binding affinities of the compounds with the active sites of the target proteins. To establish structure activity relationship (SAR), pharmacophore studies have been carried out to investigate the key pharmacophore features of the structures of the compounds responsible for biological activities.