Synthesis of Purine-Based Ionic Liquids and Their Applications


Bio-based ionic liquids (ILs) are being increasingly sought after, as they are more sustainable and eco-friendly. Purines are the most widely distributed, naturally occurring N-heterocycles, but their low water-solubility limits their application. In this work, four purines (theobromine, theophylline, xanthine, and uric acid) were combined with the cation tetrabutylammonium to synthesize bio-based ILs. The physico-chemical properties of the purine-based ILs were characterized, including their melting and decomposition temperatures and water-solubility. The ecotoxicity against the microalgae Raphidocelis subcapitata was also determined. The ILs show good thermal stability (> 457 K) and an aqueous solubility enhancement ranging from 53- to 870-fold, in comparison to their respective purine percursors, unlocking new prospects for their application where aqueous solutions are demanded. The ecotoxicity of these ILs seems to be dominated by the cation, and it is similar to chloride-based IL, emphasizing that the use of natural anions does not necessarily translate to more benign ILs. The application of the novel ILs in the formation of aqueous biphasic systems (ABS), and as solubility enhancers, was also evaluated. The ILs were able to form ABS with sodium sulfate and tripotassium citrate salts. The development of thermoresponsive ABS, using sodium sulfate as a salting-out agent, was accomplished, with the ILs having different thermosensitivities. In addition, the purine-based ILs acted as solubility enhancers of ferulic acid in aqueous solution.



subject category

Biochemistry & Molecular Biology; Chemistry, Multidisciplinary


Carreira, ARF; Veloso, T; Schaeffer, N; Pereira, JL; Ventura, SPM; Rizzi, C; Plenet, JS; Passos, H; Coutinho, JAP

our authors


This work was developed within the scope of the project CICECO-Aveiro Institute of Materials and CESAM (UIDB/50011/2020 and UIDP/50011/2020, as well as UIDP/50017/2020 and UIDB/50017/2020, respectively), financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. This work was also funded by national funds, through the Portuguese Foundation for Science and Technology, within the scope of the bilateral Portuguese-French program Hubert Curien (Pessoa). Ana R. F. Carreira and Telma Veloso acknowledge FCT for the Ph.D. grants SFRH/BD/143612/2019 and SFRH/BD/147346/2019, respectively. N.S. acknowledges the national funds (OE), through FCT-Fundacao para a Ciencia e a Tecnologia, I. P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of 29 August, changed by Law57/2017, of 19 July. H. Passos acknowledges FCT-Fundacao para a Ciencia e a Tecnologia, I.P., for the researcher contract CEECIND/00831/2017, under the Scientific Employment Stimulus-Individual Call, 2017.

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