Exploring anticancer and antibacterial activities of two self-assembling units: Band gap calculations, DFT studies, and polymorphism of a carbohydrazone ligand

The synthesis and physicochemical characterization of a novel self-assembling unit 1,3-bis(4-hydroxyphenylmethylideneamino)guanidine hydrochloride (H₅L¹) and polymorphic crystal structures of an analogous proligand 1,5-bis(4-hydroxybenzaldehyde) carbohydrazone (H₄L². DMF & H₄L². H₂O) are reported. The crystal systems of H₄L². DMF and H₄L². H₂O are monoclinic with C2/c and P2₁/c space groups. The intermolecular contacts are calculated by Hirshfeld surface analyses, which reveal that H···H interactions have a maximum contribution in the total Hirshfeld surfaces in both the crystal structures. The study also signifies that hydrogen bonding interactions are dominant in the crystal lattice of H₄L². H₂O, while the C–H∙∙∙π interactions are also significant in H₄L². DMF lattice. Density functional theory is used for optimizing geometry and calculating quantum chemical parameters. Theoretical frontier molecular energy gaps in the gas phase for H₅L¹ and H₄L² are found to be 3.49 and 4.09 eV respectively. The solid-state band gaps of H₅L¹ and H₄L² are determined experimentally using the Kubelka-Munk model and are found to be 2.72 and 2.43 eV respectively, which is indicative of strong intermolecular association in the solid lattice of H₄L². ADME properties are estimated to predict the drug-likeness of the compounds. In vitro antibacterial activity study reveals that the diaminoguanidine based proligand is a more efficient inhibitor against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacterial species. Also, in vitro study of the compounds against human breast cancer MCF-7 cells shows that with the increase in the concentrations of the compounds the percentage of cell viability decreases, which indicates the anticancer potentials of both compounds. The IC₅₀ values of H₅L¹ and H₄L² against MCF-7 cell lines (205.62 and 247.31 µg/mL) are also found to be better compared to the same (274.59 and 375.45 µg/mL) against the non-cancerous Mouse Fibroblast (L929) cell lines.