Structural Design of Ionic Liquids for Optimizing Aromatic Dissolution

Bulk Nanostructure of Mixtures of Choline Arginate, Choline Lysinate, and Water

Neutron diffraction with empirical potential structure refinement was used to investigate the bulk liquid nanostructure of mixtures of choline arginate (Ch[Arg]), choline lysinate (Ch[Lys]), and water at mole ratios of 1Ch[Arg]:1Ch[Lys]:6H2O (balanced), 1Ch[Arg]:1Ch[Lys]:20H2O (balanced dilute), 3Ch[Arg]:1Ch[Lys]:12H2O (Arg- rich), and 1Ch[Arg]:3Ch[Lys]:12H2O (Lys- rich). The Arg- and Lys- anions tend not to associate due to electrostatic repulsion between charge groups and weak anion-anion attractions. This means that the local ion structures around the anions in these mixtures resemble the parent single-component systems. The bulk liquid nanostructure varies with the Arg-:Lys- ratio. In the Lys--rich mixture (1Ch[Arg]:3Ch[Lys]:12H2O), Lys- side chains cluster into a continuous apolar domain separated from a charged domain of polar groups. In the balanced mixture (1Ch[Arg]:1Ch[Lys]:6H2O), Lys- side chains form discrete apolar aggregates within a continuous polar domain of Arg-, Ch+, and water, and in the Arg--rich mixture (3Ch[Arg]:1Ch[Lys]:12H2O), the distribution of Lys- and Arg- is nearly homogeneous. Finally, in the balance dilute system (1Ch[Arg]:1Ch[Lys]:20H2O), a percolating water domain forms.

Conformation of poly(ethylene glycol) in aqueous cholinium amino acid hybrid solvents

HYPOTHESIS

Hybrid solvents based on cholinium amino acid ionic liquids ([Ch][AA] ILs) mixed with water are environmentally benign solvents with low toxicity. [Ch][AA] ILs are used in biomass pretreatment processes to dissolve targeted (macro)molecules such as lignin from lingnocellulose. Understanding how [Ch][AA] ILs dissolve polymers is therefore of great interest for the rational design of ILs towards industrial application. Variation of the IL anion and the water concentration are hypothesised to change the solvent properties of [Ch][AA] hybrid solvents. Therefore, we probe the solvent quality of [Ch][AA] aqueous solutions with different anions (glycinate, prolinate and argininate) and water concentration for the simple model solute poly(ethylene glycol) (PEG).

EXPERIMENTS

Partial phase diagrams were produced to probe the salting-out effect of [Ch][AA] ILs towards PEG (M_w = 38 kDa). Small-angle neutron scattering experiments of deuterated PEG in hydrogenous [Ch][AA] aqueous solutions were performed to determine the polymer radius of gyration at infinite dilution (R_g,0) via Zimm-plots. Polymer concentration dependent apparent R_g values were obtained fitting an excluded volume polymer model onto the scattering data. Blends of hydrogenous and deuterated PEG under zero average contrast conditions were analysed to probe R_g at high polymer concentrations.

FINDINGS

Hydrogen bond capacity of the anion is key to the salting-out effect of [Ch][AA] ILs on PEG. R_g,0 depends on anion species and water concentration. At IL:water = 1:30 (mole:mole) and 37 °C, cholinium argininate and cholinium glycinate are close to theta solvents while cholinium prolinate and dilute cholinium argininate (IL:water = 1:100) are between theta and good solvents.

Triazine bis(pyridinium) hydrogen sulfate ionic liquid immobillized on functionalized halloysite nanotubes as an efficient catalyst for one-pot synthesis of naphthopyranopyrimidines

1,1′-(6-(Propyl amino)-1,3,5-triazine-2,4-diyl)bis(pyridinium) hydrogen sulfate immobillized on halloysite nanotubes [(PATDBP)(HSO₄)₂@HNT] as a solid acid nanocatalyst was successfully synthesized and characterized by various analysis techniques such as FT-IR, TGA, SEM/EDX, elemental mapping, TEM and elemental analysis. This catalyst was found to be highly efficient for the convenient synthesis of naphthopyranopyrimidine derivatives through a one-pot three-component reaction of β-naphthol, aldehydes and N,N-dimethylbarbituric acid in excellent yields under solvent-free conditions. Furthermore, the catalyst could be recovered and reused five times without any notable loss of its activity.

A novel method for synthesis of naphthopyranopyrimidines, using [(PATDBP)(HSO₄)₂@HNT] as a green and reusable catalyst is reported.

Catanionic Surfactant Self-Assembly in Protic Ionic Liquids

Mixing of cationic and anionic surfactants in water can result in pseudo-double-tailed catanionic surfactant ion pairs that form lamellar phases or vesicles that are unstable toward electrolyte addition. Here we show that despite the very high ionic strengths, catanionic surfactants counterintuitively form a wider variety of self-assembled aggregates in pure ionic liquids (ILs, pure salts in a liquid phase) than in water, including micelles, vesicles, and lyotropic phases. Self-assembled structures only form when the IL is sufficiently polar to drive self-assembly through electrostatic interactions and/or H-bond networks, but the catanionic effect is manifested only when the IL does not itself exhibit pronounced amphiphilic nanostructure. This enables the type of catanionic aggregate formed to be designed by changing the hydrogen bonds between the ions through variation of the structures of the cation and anion. These results reveal an entirely new way of controlling catanionic surfactant self-assembly under nonaqueous and high-salt conditions.

Solvation properties of protic ionic liquids and molecular solvents

Ionic liquids (ILs) are highly tailorable solvents with many potential applications. Knowledge about their solvation properties is highly beneficial in the utilization of ILs for specific tasks, though for many ILs this is currently unknown.

A methanol and protic ionic liquid Ugi multicomponent reaction path to cytotoxic α-phenylacetamido amides

The Ugi four component reaction of an aldehyde, amine, isocyanide and an ethanoic acid was effected smoothly in protic ionic liquids ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) to afford analogues of α-phenylacetamido amides in good to excellent isolated yields. The corresponding reactions in [BMIM][PF₆] and the protic ionic liquid ethanolammonium nitrate (ETAN) failed. Microwave irradiation in EAN facilitated rapid access to three focused libraries, based on the parent isocyanide: cyclohexyl isocyanide, benzyl isocyanide and ethyl isocyanoacetate. Analysis of the structure activity relationship data suggested the presence of a bulky moiety originating from the isocyanide (cyclohexyl and benzyl) enhanced cytotoxicity. Removal of the acetylenic H-atom from the ethanoic acid moiety was detrimental to cytotoxicity. The most active analogues produced, N-(2-cyclohexylamino)-1-(4-methoxyphenyl)-2-oxoethyl-N-(3,5-dimethoxyphenyl)propiolamide, returned average GI₅₀ values of ≤1 μM across the cancer cell lines evaluated. Combined, these data suggest that analogues of this nature are interesting potential anti-cancer development leads.

The Ugi reaction (aldehyde, amine, isocyanide and an ethanoic acid) in the protic ionic liquids ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) gave excellent yields of α-phenylacetamido amides.