Biocompatible Deep Eutectic Solvents from Diethylammonium Chloride and Urea: Evaluation of Antioxidant Efficiency and Phytotoxicity

Abstract Since revealing the importance of reline DES (a eutectic mixture of choline chloride and urea at a 1:2 molar ratio), in the past few years, a huge number of such types of eutectic mixtures have been discovered. In the present work, diethylammonium chloride salt, synthesized by the treatment of diethylamine with concentrated hydrochloric acid, was blended with urea into various molar ratios, resulting in novel eutectic mixtures with varying characteristics and stabilities, followed by the optimization of experimental protocols (concentration, time, temperature, microwave irradiation). These new SU‐based DESs were thin, stable, and clear liquids and were obtained by two combinations of S1U1 and S1U2 in an oil bath. These DESs were screened for their in vitro biological potential through phytotoxicity, and 1,1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) assays in which they were found to be potent antioxidants, even stronger than reference ascorbic acid, as well as phytotoxic substances. The DFT/PBE1PBE approaches, in combination with the 6–31 + G(d) basis set, expedite the determination of optimized geometrical parameters for the screened DESs. Furthermore, investigations into intermolecular interactions utilizing the independent gradient model‐Hirshfeld (IGM‐Hirshfeld) approach and atoms in molecules (AIM) and reduced density gradient (RDG) isosurface studies provided insights into electrostatic interactions among the synthesized DESs.