Molecular Insight into the Structural Properties of Deep Eutectic Solvents Based on Alkanolamines-A Theoretical and Experimental Study.

Molecular dynamics simulations were performed on 27 deep eutectic solvents (DESs) composed of various hydrogen bond acceptors (HBAs)-tetrabutylammonium bromide (TBAB), tetrabutylammonium chloride (TBAC), and tetraethylammonium chloride (TEAC)-combined with different hydrogen bond donors (HBDs)-3-aminopropan-1-ol (AP), 2-(methyl-amino)ethanol (MAE), and 2-(n-butylamino)ethanol (BAE). Radial distribution functions (RDFs) were computed from the simulation trajectories to probe the microscopic structure of these DESs. The effects of HBA/HBD molar ratio, alkyl chain length, anion type, and the amine group's substitution on the structural organization of the DESs were systematically investigated. Moreover, the influence of water addition on the structural properties of selected DESs (TBAB with AP, MAE, or BAE at a 1:6 molar ratio) was explored. These structural features were then correlated with previously reported experimental data. To complement the classical simulations, ab initio molecular dynamics simulations were conducted on the same TBAB-based systems, enabling the analysis of electronic structure phenomena, including RDFs, dipole moment distributions, and charge transfer. Furthermore, experimental large-angle X-ray scattering (LAXS) data collection and analysis were performed in terms of the simulated structural data. This multi-scale approach provides a detailed understanding of the structural and electronic characteristics governing the behavior of alkanolamine-based DES.