Karolina Matuszek

Tailoring ionic liquid catalysts: structure, acidity and catalytic activity of protonic ionic liquids based on anionic clusters, [(HSO4)(H2SO4)x]− (x = 0, 1, or 2)

Aiming at inexpensive Bronsted-acidic ionic liquids, suitable for industrial-scale catalysis, a family of protonic ionic liquids based on nitrogen bases and sulfuric acid has been developed. Variation of the molar ratio of sulfuric acid, χH2SO4, was used to tune acidity. The liquid structure was studied using 1H NMR and IR spectroscopies, revealing the existence of hydrogen-bonded clusters, [(HSO4)(H2SO4)]−, for χH2SO4 > 0.50. Acidity, quantified by Gutmann Acceptor Number (AN), was found to be closely related to the liquid structure. The ionic liquids were employed as acid catalysts in a model reaction; Fischer esterification of acetic acid with 1-butanol. The reaction rate depended on two factors; for χH2SO4 > 0.50, the key parameter was acidity (expressed as AN value), while for χH2SO4 > 0.50 it was the mass transport (solubility of starting materials in the ionic liquid phase). Building on this insight, the ionic liquid catalyst and reaction conditions have been chosen. Conversion values of over 95% were achieved under exceptionally mild conditions, and using an inexpensive ionic liquid, which could be recycled up to eight times without diminution in conversion or selectivity. It has been demonstrated how structural studies can underpin rational design and development of an ionic liquid catalyst, and in turn lead to a both greener and economically viable process.

Hydrogen-bond-rich ionic liquids as effective organocatalysts for Diels–Alder reactions

The synthesis and characterisation of new hydrogen-bond-rich ionic liquids and studies of their catalytic performance in Diels–Alder reactions are described. D-Glucose and chloroalcohols were used as the raw materials and as the sources of hydroxyl groups for the synthesis of ionic-liquid cations, whereas weakly coordinating bis(trifluoromethylsulfonyl)imide was used as the anion. The new ionic liquids were analysed by 1H and 13C NMR spectroscopy and by ESI-MS experiments, which confirmed their structures. In addition, the thermal data of the studied ionic liquids measured by differential scanning calorimetry and thermogravimetric analysis showed that these compounds tend to form a glass at temperatures in the range of −29 °C to −16 °C and are thermally stable from ambient temperature to at least 430 °C, most likely because of the presence of bis(trifluoromethylsulfonyl)imide anions. The performance of the ionic liquids in the model reaction of cyclopentadiene with diethyl maleate or methyl acrylate was investigated. The studied ionic liquids showed high activity even when present in catalytic amounts (4 mol% with respect to the dienophile). An increase in the number of hydroxyl groups present in the ionic liquid structure resulted in higher reaction rates.

Friedel–Crafts alkylation catalysed by GaCl3-based liquid coordination complexes

Friedel–Crafts alkylation of benzene with 1-decene was catalysed by a new family of liquid Lewis acids: liquid coordination complexes (LCCs). LCCs are prepared by mixing a metal halide (e.g. GaCl3) and a donor molecule (e.g. N,N-dimethylacetamide, urea, or trioctylphosphine oxide), with the metal halide typically used in excess. This leads to the formation of a eutectic mixture comprised of charged and neutral species in a dynamic equilibrium. GaCl3-based LCCs were used in catalytic amounts, giving high reaction rates under ambient conditions, with selectivities to 2-phenyldecane superior to those previously reported in the literature. The influence of reaction conditions and catalyst composition on the reaction rate and selectivity was investigated. Optimised reaction conditions were suggested. This exploratory study offers promise with regard to the development of safer, LCC-based alternatives to HF in industrial alkylations.

New strategies for the synthesis of lactones using peroxymonosulphate salts, ionic liquids and microwave or ultrasound irradiation

A new method for the rapid synthesis of lactones via the one-pot oxidation of alcohols with potassium peroxymonosulphate in an ionic liquid was developed. The use of microwave or ultrasonic irradiation increased the reaction rates significantly. Additionally, new peroxymonosulphate ionic liquids were synthesised and used as effective oxidants in the synthesis of lactones.

Borenium ionic liquids as catalysts for Diels–Alder reaction: tuneable Lewis superacids for catalytic applications

Ionic liquids based on the tricoordinate borenium cation were used for the first time as Lewis acid catalysts for a model Diels–Alder reaction. The conversion of the dienophile was successfully correlated with the Gutmann acceptor number values of the ionic liquids. Borenium ionic liquids exceeded the performance of catalysts reported in the literature.

Exceptional activity of gallium(III) chloride and chlorogallate(III) ionic liquids for Baeyer–Villiger oxidation

Baeyer–Villiger oxidation of cyclic ketones, using H2O2 as the oxidising agent, was systematically studied using a range of metal chlorides in different solvents, and in neat chlorogallate(III) ionic liquids. The extremely high activity of GaCl3 in promoting oxidation with H2O2, irrespective of solvent, was reported for the first time. The activity of all other metal chlorides was strongly solvent-dependent. In particular, AlCl3 was very active in a protic solvent (ethanol), and tin chlorides, SnCl4 and SnCl2, were active in aprotic solvents (toluene and dioxane). In order to eliminate the need for volatile organic solvent, a Lewis acidic chlorogallate(III) ionic liquid was used in the place of GaCl3, which afforded typically 89–94% yields of lactones in 1–120 min, at ambient conditions. Raman and 71Ga NMR spectroscopic studies suggest that the active species, in both GaCl3 and chlorogallate(III) ionic liquid systems, are chlorohydroxygallate(III) anions, [GaCl3OH]−, which are the products of partial hydrolysis of GaCl3 and chlorogallate(III) anions; therefore, the presence of water is crucial.

Silica-supported chlorometallate(III) ionic liquids as recyclable catalysts for Diels–Alder reaction under solventless conditions

A range of Lewis acidic metal chlorides were tested as homogeneous catalysts in a model Diels–Alder reaction; AlCl3 and GaCl3 performed best in terms of conversion and endo:exo selectivity. Based on this outcome, the corresponding chlorometallate(III) ionic liquids were tested as homogeneous catalysts, without a decrease in performance compared to the chlorides. Finally, these ionic liquids were heterogenised by covalent tethering of the cation onto a multimodal porous silica support; such supported chlorogallate(III) ionic liquids are reported for the first time. Supported chlorometallate(III) ionic liquids were used as recyclable heterogeneous catalysts for the Diels–Alder reaction under solventless conditions. High yields (99%) and high endo-selectivities (95%) were obtained after very short reaction times (5 min) at near-ambient temperature (25 °C).

Studies on the radical polymerization of monomeric ionic liquids: nanostructure ordering as a key factor controlling the reaction and properties of nascent polymers

In this paper, the kinetics of the radical polymerization of two monomeric ionic liquids: 1-ethyl- and 1-butyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide ([evim][NTf2] and [bvim][NTf2], respectively) as well as the molecular dynamics of the obtained polymers were investigated by means of Broadband Dielectric Spectroscopy (BDS), Fourier Transform Infra-Red (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). We propose a novel method of dielectric data analysis, to extract information on the progress of polymerization in highly conductive materials. It was found that the progress of reaction can be easily monitored by measuring the time evolution of dc conductivity, which correlates very well with the monomer conversion estimated from calorimetric or FTIR investigations. Additionally, it is clearly shown that even a small modification in the chemical structure, i.e. the length of the alkyl substituent, of monomeric ionic liquids leads to a dramatic change in the properties of the produced polymers. The obtained results are discussed in light of recent studies indicating a completely different tendency to nanostructure ordering in the investigated monomeric ionic liquids.

A versatile method of epoxide formation with the support of peroxy ionic liquids

The application of the peroxy ionic liquid, 1-butyl-3-methylimidazolium peroxymonosulphate, as an oxidation agent and a solvent for the synthesis of epoxides was described. The 2.5-molar excess of the peroxy ionic liquid to olefin was applied. The reaction system consisted of 1,1,1-trifluoroacetone as an oxirane precursor, which was used with the molar ratio of 1 : 3 relative to olefin and water solution of NaHCO3. Under these conditions the epoxidation of 4-bromocinnamic acid led to the epoxide formation at the ambient temperature in 30 minutes. Dioxiranes, generated from the peroxy ionic liquid and 1,1,1-trifluoroacetone, demonstrated encouraging potential for the epoxidation of a variety of other olefins: styrene, limonene, stilbene, linalyl acetate and a complex steroid molecule with high yields of final epoxides from 65–98%.

Electrodeposition of Zinc Coatings from Ionic Liquid

The electrochemical deposition of zinc coatings from 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) baths on steel substrate was described in this paper. The influence of [ZnCl2]/[BMIMCl] ratio, current density as well as temperature have been investigated. It was found that electrodeposition in all of tested baths and parameters allowed to obtain zinc coatings. The surface of coatings were matte and in the most of cases the coating morphology was not homogenous. On the basis of corrosion investigation it was pointed out that application of the baths of higher ZnCl2 content are more beneficial for zinc coatings electrodeposition that the one of [ZnCl2]/[BMIMCl]= 2:3.