Solvent-free click chemistry for tetrazole synthesis from 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-Based fluorinated ionic liquids, their micellization, and density functional theory studies

Abstract

In the present study, we have synthesized novel 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-based fluorinated ILs (DBUF-ILs) simply by solvent-free quaternization and subsequent anion (F⁻) exchange reactions. The micellization behavior and density functional theory (DFT) calculations of DBUF-ILs have been conducted. The DFT calculations of some selected DBU derivatives show the N-substitution effect on DBU geometry. In addition to the geometry analysis of these DBU derivatives, HOMO and LUMO energies, and band gaps were also calculated which give insight into different types of transitions and electronic effects. The stability of the DBU derivatives was also investigated via binding energy calculations based on the DFT method. A click chemistry reaction for tetrazole formation is performed under solvent-free thermal and microwave irradiation. The yields obtained were in the range of 70–95%. Complete structural characterization of each product was accomplished by several modern techniques including ¹H NMR, ¹³C NMR, EI⁺ and/or FAB mass spectrometry, IR and UV spectroscopy.