In silico investigation of the microscopic structural features of a glucose-based deep eutectic solvent

Abstract

Atomistically detailed force field is used to investigate the microscopic structure of a naturally abundant deep eutectic solvent (NADES) composed of glucose, urea, and water in a 6 : 4 : 1 mass ratio at 328 K. The spatial distribution of the constituent molecules is analysed using pair correlation functions and by classifying the types of triangular spaces formed by three randomly chosen molecules. Key structural features such as water molecule clustering, relative orientation of urea molecular planes, and statistics of multi-hydrogen bonded electronegative atoms are also reported. The analysis reveals predominance of asymmetrically spaced molecules, with very few instances of symmetrical arrangements, such as molecular positioning at the vertices of equilateral or isosceles triangles. We also report significant deviations in the water structure from tetrahedrality, with water mostly existing in clusters of 4 to 5 molecules. Urea molecules predominantly adopt orthogonal relative orientations, a behaviour primarily driven by steric hindrance resulting from molecular crowding. Finally, strong hydrogen bond interactions between water and glucose are observed, with water oxygen atoms typically forming 2 to 3 hydrogen bonds, while glucose oxygen atoms form 1 to 2. In contrast, urea–urea interactions are favoured over interactions with glucose or water, with urea–water hydrogen bonding being the least preferred.