Thermodynamics of complexation of cesium with dibenzo-21-crown-7 and dibenzo-24-crown-8 in 1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide

The stability constants of the cesium complexes [Cs(DB21C7)] + and [Cs(DB24C8)] + , where DB21C7 = dibenzo-21-crown-7 and DB24C8 = dibenzo-24-crown-8, in the hydrophobic ionic liquid 1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([BMIM][N(Tf) 2 ]) have been measured by 133 Cs NMR spectroscopy between 24 and 54°C. The enthalpies and entropies of complexation have been determined. For [Cs(DB21C7)] + and [Cs(DB24C8)] + at 25°C, log K 1 = 3.52 (0.01) and 2.91 (0.04), Δ H 1 = −27 (1) and −7 (6) /mol, and Δ S 1 = −23 (3) and 33 (20) J/(mol K), respectively.