Chain length and OH-spacing effects on diol-based deep eutectic solvents

Since their conceptualization in 2004, the study of deep eutectic solvents (DESs) has greatly advanced over the last two decades. One of the more popular DESs is ethaline, a system made up of choline chloride (ChCl) as a hydrogen bond acceptor (HBA) and ethylene glycol as a hydrogen bond donor (HBD). Ethaline has been extensively studied over the years due to its many advantages. Besides ethylene glycol, other diol HBDs have been suggested and compared to the ethaline systems. In this work, DES systems using 1,2-propanediol and 1,3-propanediol as HBDs have been measured to study their conductivity, viscosity, density, polarity on the ET(30) scale, and solvent response dynamics by femtosecond transient absorption (fs-TA) spectroscopy. In addition to experimental measurements, classical molecular dynamics simulations were performed to further understand solvation structures and hydrogen bond networks. The effects of the alkyl chain length and O–H spacing on the mentioned parameters was determined.