{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,10]],"date-time":"2026-02-10T20:21:36Z","timestamp":1770754896165,"version":"3.50.0"},"reference-count":73,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2021,11,18]],"date-time":"2021-11-18T00:00:00Z","timestamp":1637193600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["UIDB\/50011\/2020, UIDP\/50011\/2020, UIDP\/50017\/2020, UIDB\/50017\/2020"],"award-info":[{"award-number":["UIDB\/50011\/2020, UIDP\/50011\/2020, UIDP\/50017\/2020, UIDB\/50017\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["Portuguese-French program Hubert Curien (Pessoa)"],"award-info":[{"award-number":["Portuguese-French program Hubert Curien (Pessoa)"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["SFRH\/BD\/143612\/2019"],"award-info":[{"award-number":["SFRH\/BD\/143612\/2019"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["SFRH\/BD\/147346\/2019"],"award-info":[{"award-number":["SFRH\/BD\/147346\/2019"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e Tecnologia","doi-asserted-by":"publisher","award":["CEECIND\/00831\/2017"],"award-info":[{"award-number":["CEECIND\/00831\/2017"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>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\u2013chemical 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 (&gt;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.<\/jats:p>","DOI":"10.3390\/molecules26226958","type":"journal-article","created":{"date-parts":[[2021,11,19]],"date-time":"2021-11-19T02:43:09Z","timestamp":1637289789000},"page":"6958","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Synthesis of Purine-Based Ionic Liquids and Their Applications"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8983-9202","authenticated-orcid":false,"given":"Ana R. F.","family":"Carreira","sequence":"first","affiliation":[{"name":"Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"given":"Telma","family":"Veloso","sequence":"additional","affiliation":[{"name":"Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"},{"name":"Department of Biology & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0747-2532","authenticated-orcid":false,"given":"Nicolas","family":"Schaeffer","sequence":"additional","affiliation":[{"name":"Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7573-6184","authenticated-orcid":false,"given":"Joana L.","family":"Pereira","sequence":"additional","affiliation":[{"name":"Department of Biology & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9049-4267","authenticated-orcid":false,"given":"S\u00f3nia P. M.","family":"Ventura","sequence":"additional","affiliation":[{"name":"Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0108-3800","authenticated-orcid":false,"given":"C\u00e9cile","family":"Rizzi","sequence":"additional","affiliation":[{"name":"Laboratoire Physico-Chimie des \u00c9lectrolytes et Nano-Syst\u00e8mes Interfaciaux, PHENIX, CNRS, Sorbonne Universit\u00e9, F-75005 Paris, France"}]},{"given":"Juliette","family":"Sirieix Pl\u00e9net","sequence":"additional","affiliation":[{"name":"Laboratoire Physico-Chimie des \u00c9lectrolytes et Nano-Syst\u00e8mes Interfaciaux, PHENIX, CNRS, Sorbonne Universit\u00e9, F-75005 Paris, France"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0573-093X","authenticated-orcid":false,"given":"Helena","family":"Passos","sequence":"additional","affiliation":[{"name":"Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3841-743X","authenticated-orcid":false,"given":"Jo\u00e3o A. P.","family":"Coutinho","sequence":"additional","affiliation":[{"name":"Department of Chemistry, CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.aca.2009.12.007","article-title":"Ionic liquids in analytical chemistry","volume":"661","author":"Sun","year":"2010","journal-title":"Anal. Chim. Acta"},{"key":"ref_2","first-page":"405","article-title":"Molecular weights and electrical conductivity of several fused salts","volume":"8","author":"Walden","year":"1914","journal-title":"Bull. Acad. Imper. Sci."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"115069","DOI":"10.1016\/j.molliq.2020.115069","article-title":"The unseen evidence of Reduced Ionicity: The elephant in (the) room temperature ionic liquids","volume":"324","author":"Mariani","year":"2021","journal-title":"J. Mol. 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