The formation of deep eutectic solvents (DES) is tied to negative deviations to ideality
caused by the establishment of stronger interactions in the mixture than in the pure DES precursors.
This work tested thymol and menthol as hydrogen bond donors when combined with different
flavonoids. Negative deviations from ideality were observed upon mixing thymol with either
flavone or flavanone, two parent flavonoids that only have hydrogen bond acceptor (HBA) groups,
thus forming non-ionic DES (Type V). On the other hand, the menthol systems with the same
compounds generally showed positive deviations from ideality. That was also the case with the
mixtures containing the more complex hydroxylated flavonoid, hesperetin, which resulted in positive
deviations when mixed with either thymol or menthol. COSMO-RS successfully predicted the
behavior of the solid-liquid phase diagram of the studied systems, allowing for evaluation of the
impact of the different contributions to the intermolecular interactions, and proving to be a good tool
for the design of DES.
This research was developed within the scope of the project CICECO-Aveiro Institute of
Materials, UIDB/50011/2020, UIDP/50011/2020, and LA/P/0006/2020, and project CIMO-Mountain
Research Center, UIDB/00690/2020 and LA/P/0007/2020, financed by national funds through the
Portuguese Foundation for Science and Technology/MCTES. Support was also provided by project
AllNat—POCI-01-0145-FEDER-030463 (PTDC/EQU-EPQ/30463/2017), funded by FEDER funds
through COMPETE2020—Prog. Operacional Competitividade e Internacionalização (POCI), and
by national funds through the Foundation for Science and Technology (FCT/MCTES). This work
was supported by the Fundacão para a Ciência e Tecnologia (FCT) (funded by national funds
through the FCT/MCTES (PIDDAC)) to CIQUP, Faculty of Science, University of Porto (Project
UIDB/00081/2020), IMS-Institute of Molecular Sciences (LA/P/0056/2020)). A.I.M.C.L.F. is financed
by national funds through the FCT-I.P., in the framework of the execution of the program contract
provided in paragraphs 4, 5, and 6 of art. 23 of Law no. 57/2016 of 29 August, as amended by
Law no. 57/2017 of 19 July. G.T. and S.M.V.B. acknowledge FCT/MCTES for the Ph.D. grants
UI/BD/151114/2021 and SFRH/BD/138149/ 2018, respectively.
