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Polarity of Some [NR 1 R 2 R 3 R 4 ] + [Tf 2 N] − Ionic Liquids in Ethanol: Preferential Solvation versus Solvent–Solvent Interactions

2012; American Chemical Society; Volume: 57; Issue: 10 Linguagem: Inglês

10.1021/je300563k

1520-5134

Maria-Luísa C.J. Moita, Ângela F.S. Santos, João F. C. C. Silva, Isabel M. S. Lampreia,

Photochemistry and Electron Transfer Studies

The polarity of the ionic liquids [N4111][Tf2N], [N4441][Tf2N], and [choline][Tf2N], as well as their binary mixtures with ethanol has been investigated using solvatochromic dyes and expressed in terms of the Reichardt parameter, ETN, and the Kamlet–Taft parameters (π*, α, and β), at 298.15 K. The synergetic behavior revealed essentially by the ethanol + [N4441][Tf2N] system for the acidity of the solvent shows the potential importance of this solvent media for some chemical applications. Even though the preferential solvation model of Bosch and co-workers has been applied with some statistical success to the whole composition range of EtOH + [N4111][Tf2N] and EtOH + [N4441][Tf2N] binary mixtures, the interpretation of the results is somehow difficult due to the competition of molecular interactions in the evaluation of transition energies for the pairs: dye–solvent (dye–cation and/or dye–anion, dye–EtOH, dye–complex entity) and cation–anion, depending on the composition range. Different patterns of solvent polarity behavior are shown along the entire ionic liquid (IL) composition.