Synthesis, characterization, and physicochemical properties of three new nanostructured benzimidazole-based dicationic Brønsted acidic molten salts and comparison of their catalytic and antibacterial activities

Abstract

In the present study, three novel dicationic Brønsted acidic molten salts based on benzimidazole were synthesized and characterized by FT-IR, 1HNMR, 13CNMR and FESEM techniques. Topological analysis of the atoms in molecules (AIM), electron localization function (ELF), Mayer bond index and local aromaticity analysis were applied to study the theoretical and electronic structure of the presented molten salts molecules, and the nature of C-N, N-H, N-S, O-H, and H-Cl bonding was investigated. Antibacterial activities of the molten salts were tested against the Bacillus subtilis (Gram-positive) and Escherichia coli (Gram-negative) by the agar well diffusion method. The catalytic activity of the novel salts was also assessed using two different one-pot multi-component reactions in two various media (in the presence and absence of solvent) for the promotion of the synthesis of pyrano[2,3-d]-pyrimidinone and polyhydroquinoline derivatives. In this study, also the acidity of molten salts (by determination of their Hammett acidity function (H0) and potentiometric titration method) and its effect on their catalytic activity was investigated. Easy preparation of the reagents, reusability, green process, simple work-up procedure, high yields, and short reaction times are the most important advantages of the application of these salts as catalysts.