Equilibrium partitioning of drug molecules between aqueous and amino acid ester-based ionic liquids

In this work, a series of novel room temperature ionic liquids (ILs) have been synthesized with cheap, naturally alpha-amino acid ester as cations and bis(trifluoromethylsulfonyl)imide as anion. The glass transition temperature and thermal decomposition temperature of these ILs, partition coefficients of some coumarins and purine alkaloids between water and the amino acid ester-based ILs at T = 298.15 K, and Gibbs energy, enthalpy and entropy changes for the transfer of caffeine and 6,7-dihydroxycoumarin from water to [LeuC(2)][Tf2N] have been determined. It is shown that these ILs are highly effective materials for the extraction of drug compounds like coumarin, 4-hydroxycoumarin, 7-hydroxycoumarin, 3-aminocoumarin, coumarin-3-carboxylic acid, 6,7-dihydroxycoumarin, 6,7-dihydroxy-4-methylcoumarin, caffeine, theobromine, theophylline, inosine, and 2,6-diaminopurine. The partition process is driven by enthalpy term, and partition coefficients of the drug molecules increase with the increase of hydrophobicity of both the drug molecules and the ILs. Furthermore, the possible partition mechanism has been investigated from C-13 NMR measurements. (c) 2013 Elsevier Ltd. All rights reserved.