(502d) Understanding the Dissolution Mechanism of Nucleobases in Ionic Liquids: FTIR-ATR, NMR Spectra and Ab Initio Calculations Insights

Room Temperature Ionic Liquids (RTILs) are revolutionizing the world of solvents due to the unique combination of their many interesting properties. The tunable nature of the solubility of various compounds, including molecules of pharmaceutical and biological interest, in RTILs makes extraction with RTILs attractive for many separation and purification processes. Exploring new applications requires fundamental understanding of phase behavior. In the present work, we explore the use of RTILs to dissolve three selected nucleobases, uracil, thymine and adenine. Uracil is a common and naturally occurring pyrimidine derivative, found in RNA, it base pairs with adenine and replaces thymine during DNA transcription. A large set of ionic liquids displaying different physico-chemical properties was tested. FTIR and NMR spectra were used to understand the underlying mechanism of solubilisation of the two most promising RTILs, 1-ethyl-3-methylimidazolium acetate ([C₂mim][CH₃COO^-]) and 1-butyl-3-methylimidazolium acetate ([C₄mim][CH₃COO^-]). The establishment of preferential interactions simultaneously with functional groups of both the cation and the anion is the cause of this enhanced solubility. ab Initio calculations obtained using Gaussian also corroborate the spectroscopic results.