Insight of interaction in kojic acid/urea derivatives deep eutectic solvent from physicochemical characterization and computation simulation

In recent years, the excellent performance of deep eutectic solvents (DES) has garnered increasing attention in the pursuit of sustainable solvents. This study employs natural and biodegradable kojic acid (KA) as a hydrogen bond donor (HBD) and environmentally friendly urea derivatives as hydrogen bond acceptor (HBA) to construct a series of novel type V KA/urea derivatives DESs. The as-obtained DESs were systematically characterized by density, viscosity, refractive index, speed of sound, thermal gravimetric analysis, FT-IR and NMR spectrums . The behavior of components in the DESs were deduced on the basis of thermal expansion coefficient ( α P ), apparent molar volume ( V 2∅ ), free volume ( F m ), and spectroscopic analysis. The interactions in the DESs were further cross-checked by Quantum chemical calculation and molecular dynamics simulation. The consistent sequence of interaction strength in the DESs was TMU-KA > DMI-KA > DMPU-KA. For KA molecule, the hydroxyl H on ring displayed lower activity than that on the side-chain due to the dual impact of conjugation and volume repulsion effect. The obtained information can provide help for understanding structure-property relationship and exploring potential utilization for present KA/Urea DESs.