In this study, atomic level interactions of a 1:1 choline chloride (ChCl)/acetylsalicylic acid (ASA) therapeutic deep eutectic solvent (THDES) has been investigated by combining the molecular dynamics (MD), density functional theory (DFT), and spectroscopic (Raman and IR) techniques. Atom−atom radial distribution functions (RDFs) based on MD simulation reveal that hydrogen bonds are formed between Cl − ••• HO Ch + and Cl − •••HO COOH of the THDES, where Cl − works as a bridge between ASA and Ch + . Cation−anion electrostatic attractions are disrupted by highly interconnected hydrogen bonds. Cluster conformers of the THDES are isolated from MD simulation and optimized using ωB97XD/6-311++G(d,p) level of theory, in which the strongest H bonds are found among OH Ch + ••• Cl − (2.37 Å) and Cl − •••HO COOH (2.40 Å). Charge transfer calculations, using CHEPLG and NBO analysis, disclose that the charge of Cl − is reduced in the cluster structures and transferred to Ch + and ASA. Further analyses are conducted using experimental and computed spectroscopic data. These confirm the formation of the THDES as peaks for −COOH, −COOR, and −OH functional groups of ASA and ChCl are either get broadened or disappeared in the spectra of the cluster conformers. Moreover, principal component analysis (PCA) assists to understand the feature of the simulated data and confirms the formation of the THDES. Solvent selectivity triangle (SST) of solvatochromic parameters also demonstrate that this THDES has some important properties similar to ionic liquids and common deep eutectic solvent.
In this study, the quantum chemical properties, nonbonding interactions, and spectroscopic insights of a wide variety of choline chloride (ChCl)-based deep eutectic solvents were investigated employing molecular dynamics (MD), density functional theory, and spectroscopic analyses. Nine experimentally reported ChCl-based deep eutectic solvents (DESs) were selected for this study where ChCl was common in all the DESs and the hydrogen bond donors (HBDs) were varied. The most energetically favorable cluster was selected using MD simulation followed by density functional theory calculation. The most stable cluster structures were fully optimized, and their quantum chemical properties and IR spectra were computed at the ωB97XD/6-31G++(d,p) level of theory. Principal component analysis was performed to distinguish their behavioral differences and to find out if any correlation exists among the 1:1 and 1:2 clusters. The atom–atom radial distribution functions based on MD simulations revealed that several hydrogen bonds were formed among the donor and acceptor molecules. However, the most prominent hydrogen bonds were found to be N–HHBD⋯Cl− for ChCl:U, ChCl:TU, and ChCl:Ace and O–HHBD⋯Cl− for ChCl:Glu, ChCl:Ma, ChCl:Ox, ChCl:Gly, and ChCl:Phe. Both N–HHBD⋯Cl− and O–HHBD⋯Cl− were major interactions for ChCl:Pro, where Cl− worked as a bridge between Ch+ and the respective donors. In addition, the –OH of Ch+ showed strong intermolecular interactions with the acceptor groups of the donor molecules, such as C=O and O–H. This study has tried to extract a pattern of the contributions of HBDs by comparing the structural, spectroscopic, and thermodynamic properties of ChCl-based DESs, which have also been successfully correlated with the intermolecular interactions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.