Sugar-Based Ionic Liquids: Multifaceted Challenges and Intriguing Potential

Carbohydrates represent a promising option in transitioning from oil-based chemical resources to renewable ones, with the goal of developing chemistries for a sustainable future. Cellulose, hemicellulose, and largely available monosaccharides already provide useful chemical building blocks, so-called platform chemicals, such as levulinic acid and hydroxymethyl furfural, as well as solvents like cyrene or gamma-valerolactone. Therefore, there is great anticipation for novel applications involving materials and chemicals derived from sugars. In the field of ionic liquids (ILs), sugar-based ILs have been overlooked for a long time, mainly on account of their multistep demanding preparation. However, exploring new strategies for accessing sugar-based ILs, their study, and their exploitation, are attracting increasing interest. This is due to the growing concerns about the negative (eco)toxicity profile of most ILs in conjunction with their non-sustainable nature. In the present review, a literature survey concerning the development of sugar-based ILs since 2011 is presented. Their preparation strategies and thermal behavior analyses, sorted by sugar type, make up the first two sections with the intention to provide the reader with a useful guide. A final overview of the potential applications of sugar-based ILs and their future perspectives complement the present analysis.

Ion Transport Properties and Ionicity of 1,3-Dimethyl-1,2,3-Triazolium Salts with Fluorinated Anions

1,2,3-Triazolium salts are an important class of materials with a plethora of sophisticated applications. A series of three novel 1,3-dimethyl-1,2,3-triazolium salts with fluorine, containing anions of various size, is synthesized by methylation of 1,2,3-triazole. Their ion conductivity is measured by impedance spectroscopy, and the corresponding ionicities are determined by diffusion coefficients obtained from ¹H and 19F pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy data, revealing that the anion strongly influences their ion conductive properties. Since the molar ion conductivities and ionicities of the 1,3-dimethyl-1,2,3-triazolium salts are enhanced in comparison to other 1,2,3-triazolium salts with longer alkyl substituents, they are promising candidates for applications as electrolytes in electrochemical devices.

1,2,4-Triazolium ions as flexible scaffolds for the construction of polyphilic ionic liquid crystals

A novel scaffold for the construction of self-organised ionic liquids and ionic liquid crystals bearing both perfluorocarbon and hydrocarbon moieties has been developed. The phase behaviour and physical properties of these materials can be tuned as a function of chain length and fluorine content and significant structural elaboration is possible, giving a highly flexible system.

Synthesis and antioxidant action of chitosan derivatives with amino-containing groups via azide-alkyne click reaction and N-methylation

Amino functionality has been paid growing attention in chemical modification of polysaccharides due to their potential biomedical applications. Here, the preparation of novel antioxidant materials based on chitosan derivatives bearing amino-containing groups equipped with 1,2,3-triazole and 1,2,3-triazolium by Cuprous-catalyzed azide-alkyne cycloaddition and N-methylation was described for the first time. The structural characteristics of the synthesized derivatives were examined by FTIR, ¹H NMR, and elemental analysis. The antioxidant activities of the chitosan derivatives were assessed in vitro. The results indicated that chitosan derivatives bearing 1,2,3-triazoles displayed superior antioxidant activity over pristine chitosan, especially against superoxide anion radical. Moreover, antioxidant efficiency of chitosan derivatives further enhanced after N-methylation of 1,2,3-triazole moieties with iodomethane, which is comparative to that of ascorbic acid. Notably, of all chitosan derivatives bearing 1,2,3-triazole or 1,2,3-triazolium moieties, acylhydrazine-functionalized and amino-functionalized chitosan showed the stronger antioxidant capacity than hydroxyl-modified chitosan at the test concentration. Besides, the cytotoxicities of them were also evaluated in vitro on HaCaT cells. These results suggested that amino and acylhydrazine-functionalized chitosan derivatives with 1,2,3-triazolium could be used as novel antioxidant biomaterials.

Preparation of new β-D-xyloside- and β-D-xylobioside-based ionic liquids through chemical and/or enzymatic reactions

Several tetraalkylphosphonium and tetraalkylammonium salts containing xyloside- and xylobioside-based anionic moieties have been prepared. Two stereoselective routes have been developed: i) a chemical pathway in four steps from D-xylose, and ii) a chemoenzymatic pathway directly from biomass-derived xylans. These salts displayed interesting properties as ionic liquids. Their structures have been correlated to their thermal properties (melting, glass transition and decomposition temperatures).

Isohexide Dinitriles: A Versatile Family of Renewable Platform Chemicals

Building blocks of isohexides extended by one carbon atom at the 2- or 5-positions are now synthetically accessible by a convenient, selective, base-catalyzed epimerization of the corresponding dinitriles. Kinetic experiments using the strong organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) show that all three possible isohexide dinitrile isomers exist within a dynamic equilibrium. An epimerization mechanism based on density functional theory (DFT) calculations is proposed. Structural identification of all three possible isomers is based on NMR analysis and single crystal x-ray crystallography. DFT calculations confirm that the observed crystal structures are indeed the lowest energy conformers of these isohexide derivatives.

1,2,3-Triazolium-based linear ionic polyurethanes

We report the synthesis and detailed characterization of a series of ionic polyurethanes issued from the polyaddition of a 1,2,3-triazolium-functionalized diol monomer having a bis(trifluoromethylsulfonyl)imide counter-anion with four aliphatic, cycloaliphatic or aromatic commercial diisocyanates.

Enhanced Ionic Conductivity of a 1,2,3-Triazolium-Based Poly(siloxane ionic liquid) Homopolymer

A 1,2,3-triazolium-based poly(siloxane ionic liquid) (PSIL) is synthesized by UV-triggered thiol-ene ligation between a poly[(mercaptopropyl)methylsiloxane] and a tailor-made vinyl-functionalized triethylene glycol-based 1,2,3-triazolium ionic liquid. The quantitative nature of the thiol-ene coupling is demonstrated by ¹H and ¹³C NMR, whereas properties of this new PSIL are discussed based on solubility, size exclusion chromatography, differential scanning calorimetry, thermogravimetric analysis, and broadband dielectric spectroscopy measurements. Besides exhibiting low glass transition temperature (T_g = -62 °C) and high thermal stability (T_d10 = 284 °C), this new class of poly(1,2,3-triazolium) demonstrates the highest value of bulk anhydrous ionic conductivity reported to date for PILs (σ_DC = 7 × 10^-5 S cm^-1 at 30 °C).

Poly(1,2,3-triazolium)s: a new class of functional polymer electrolytes

Poly(1,2,3-triazolium)s are tunable and highly functional ion conducting materials that stretch out the actual boundaries of PILs macromolecular design.