Synthesis and Properties of Magnetic Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity.

I-Wen Sun,Che-Hsuan Yang,Jui-Cheng Chang,Tzi-Yi Wu,Wen-Yueh Ho

doi:10.3390/ma11122539

Abstract

A series of unique tunable aryl-imidazolium magnetic ionic liquids (MILs) with dual acidity that contain both Brønsted and Lewis acidic sites (abbreviated as B-L MILs) were synthesized and characterized using nuclear magnetic resonance and mass spectrometry. Physical properties, such as thermal properties, magnetic susceptibility, and Brønsted and Lewis acidity, were measured. These properties were found to depend on the cation structure. These B-L MILs had good solubility in many organic solvents, good thermal stability, and low melting points, and exhibited magnet-like behavior. For these B-L MILs, the Brønsted acidity was measured using ultraviolet-visible (UV-Vis), and the Lewis acidity was measured using Fourier transform infrared spectroscopy (FTIR). The results showed that B-L MILs with an electron-withdrawing group in the aryl-imidazolium moiety had higher Brønsted acidity, whereas those with an electron-donating group had higher Lewis acidity. This type of ionic liquid, with both Brønsted and Lewis acidic sites, is expected to be a useful solvent and catalyst for organic reactions.

Highlights

Ionic liquids (ILs) have been shown to be very promising green solvents with several general advantages such as extremely low volatility, non-flammability, low melting points, high thermal, chemical, and electrochemical stability, and extraordinary solvent properties compared to those of traditional organic solvents
Studies Materials have established a relationship between the structure and properties of ILs
The synthesis procedure and the product yields are summarized in Scheme 2

Summary

Introduction

Ionic liquids (ILs) have been shown to be very promising green solvents with several general advantages such as extremely low volatility, non-flammability, low melting points, high thermal, chemical, and electrochemical stability, and extraordinary solvent properties compared to those of traditional organic solvents. ILs are typically composed of large asymmetric organic cations and various inorganic or organic anions; the physical-chemical properties of ILs can be tuned by changing the types of cations and anions [1,2,3,4]. In addition to common ILs, many interesting ILs with special properties have been reported, such as dicationic ILs [17,18,19,20,21], polymeric ILs [13,14,22,23], magnetic ILs [24,25,26,27], and acidic ILs [28,29,30].

Methods

Results

Conclusion