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The nature of solvation of Reichardt's dye in ionic liquids is investigated through semiempirical calculations. We build on the basis of electrostatic considerations a cluster of three ionic pairs that represent the first solvation shell of the dye. The spatial organization of this shell is a balance between sterical, electrostatic and, in the case of functionalized ionic liquids, specific interactions. This model is not sufficient to obtain values of ET(30) quantitatively comparable to the experimental ones, but some qualitative features can be rationalized. The resulting scenario of solute-solvent interactions is different with respect to molecular solvents. Thus, we suggest caution in comparing ionic and molecular solvents through solvatochromic scales. [ABSTRACT FROM AUTHOR]

The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) in different room temperature ionic liquids containing imidazolium-based cations ([HBIM]+, [BMIM]+ and [BM2IM]+) has been studied at the DFT level using a supermolecular approach. An analysis of the theoretical results shows that the ionic liquid cation coordination affects the equilibrium geometries and electronic structures of the reacting species throughout the reaction pathway leading to changes in reactivity and selectivity. They also indicate that the strong asynchronicity of the Diels-Alder reactions in ionic liquids is due to the polarisation effect of the cation. [ABSTRACT FROM AUTHOR]

Some clusters of Reichardt’s dye with two ion pairs have been studied at the TD-DFT level in order to understand the effect of the ionic liquid anion on solvatochromism. Coherently with the experimental data, the anion effect results substantially related to the anion size, although generally less important than the cation effect. Only small anions, such as halogenides, show a significant effect. [ABSTRACT FROM AUTHOR]