From Salts to Ionic Liquids by Systematic Structural Modifications: A Rational Approach Towards the Efficient Modular Synthesis of Enantiopure Imidazolium Salts

Abstract

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Synthesis of Chiral Room Temperature Ionic Liquids from Amino Acids – Application in Chiral Molecular Recognition

“…In the ATR‐FTIR spectra of 7a – 12a , the bands between 3150 and 3000 cm –1 are considered diagnostic of the C–H stretching modes of the aromatic rings 6b,15. In this region, for the imidazolium aromatic ring, the vibrational bands at higher wavenumbers correspond to C6–H and C7–H stretching modes, whereas vibrational bands at lower wavenumbers correspond to the C5–H stretching mode.…”

“…CILs have additional potential as chiral solvents,12 shift reagents,13 or enantioselective catalysts 14. Furthermore, it has recently been shown that the configuration of the resulting CILs plays an important role in defining their final physical properties 15…”

“…Within this context, our group has been involved in the preparation and study of CILs prepared either from racemic materials,15 or from enantiomerically pure materials obtained from the chiral pool 16. Here we report on the preparation of a new family of CILs using natural amino acids as the source of chirality and containing an amide group as an essential structural feature.…”

Effects of substituent branching and chirality on the physical properties of ionic liquids based on cationic ruthenium sandwich complexes

“…30,31 Our study has shown that the use of racemic mixtures can be a useful strategy to lower the melting point of an ionic liquid while maintaining its chemical composition. 25 In fact, in several chiral imidazolium salts, the racemic salts have higher melting points than the enantiopure salts.…”

“…Studies on metal-containing ionic liquids 4 and protonic ionic liquids 5 with branched alkyl substituents revealed that these compounds tend to exhibit lower glass-transition temperatures and remain in the liquid state due to suppression of crystallization. 25 Chirality is an important issue in molecular compounds. However, while branched substituents often have chiral centers, relatively few studies have focused on how chirality affects the thermal properties of ionic-liquid-related materials.…”