233 results found
Sillero L, Prado R, Welton T, et al., 2021, Extraction of flavonoid compounds from bark using sustainable deep eutectic solvents, Sustainable Chemistry and Pharmacy, Vol: 24, Pages: 100544-100544, ISSN: 2352-5541
Rauber D, Philippi F, Kuttich B, et al., 2021, Curled cation structures accelerate the dynamics of ionic liquids, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 21042-21064, ISSN: 1463-9076
Chan KLA, Shalygin AS, Martyanov ON, et al., 2021, High throughput study of ionic liquids in controlled environments with FTIR spectroscopic imaging, JOURNAL OF MOLECULAR LIQUIDS, Vol: 337, ISSN: 0167-7322
Sillero L, Prado R, Welton T, et al., 2021, Energy and environmental analysis of flavonoids extraction from bark using alternative solvents, JOURNAL OF CLEANER PRODUCTION, Vol: 308, ISSN: 0959-6526
Pontillo ARN, Koutsoukos S, Welton T, et al., 2021, Investigation of the influence of natural deep eutectic solvents (NaDES) in the properties of chitosan-stabilised films, MATERIALS ADVANCES, Vol: 2, Pages: 3954-3964
Koutsoukos S, Philippi F, Malaret F, et al., 2021, A review on machine learning algorithms for the ionic liquid chemical space, CHEMICAL SCIENCE, Vol: 12, Pages: 6820-6843, ISSN: 2041-6520
Toda S, Clark R, Welton T, et al., 2021, Observation of the Pockels Effect in Ionic Liquids and Insights into the Length Scale of Potential-Induced Ordering, LANGMUIR, Vol: 37, Pages: 5193-5201, ISSN: 0743-7463
Welton T, 2021, Sustainability and international chemistry collaboration, NATIONAL SCIENCE REVIEW, Vol: 8, ISSN: 2095-5138
Philippi F, Welton T, 2021, Targeted modifications in ionic liquids from understanding to design, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 6993-7021, ISSN: 1463-9076
Bakis E, van den Bruinhorst A, Pison L, et al., 2021, Mixing divalent ionic liquids: effects of charge and side-chains, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 4624-4635, ISSN: 1463-9076
Lemus J, Santiago R, Hospital-Benito D, et al., 2021, Process Analysis of Ionic Liquid-Based Blends as H2S Absorbents: Search for Thermodynamic/Kinetic Synergies, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, Vol: 9, Pages: 2080-2088, ISSN: 2168-0485
Welton T, 2020, A big difference in diversity, Education in Chemistry, Vol: 57, ISSN: 0013-1350
Philippi F, Rauber D, Kuttich B, et al., 2020, Ether functionalisation, ion conformation and the optimisation of macroscopic properties in ionic liquids, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 22, Pages: 23038-23056, ISSN: 1463-9076
Philippi F, Pugh D, Rauber D, et al., 2020, Conformational design concepts for anions in ionic liquids, Chemical Science, Vol: 11, Pages: 6405-6422, ISSN: 2041-6520
The identification of specific design concepts for the in silico design of ionic liquids (ILs) has been accomplished using theoretical methods. Molecular building blocks, such as interchangeable functional groups, are used to design a priori new ILs which have subsequently been experimentally investigated. The conformational design concepts are developed by separately and systematically changing the central (imide), bridging (sulfonyl) and end (trifluoromethyl) group of the bis(trifluoromethanesulfonyl)imide [N(Tf)2]− anion and examining the resultant potential energy surfaces. It is shown that these design concepts can be used to tune separately the minimum energy geometry, transition state barrier height and relative stability of different conformers. The insights obtained have been used to design two novel anions for ILs, trifluoroacetyl(methylsulfonyl)imide [N(Ms)(TFA)]− and acetyl(trifluoromethanesulfonyl)imide [N(Tf)(Ac)]−. The computationally predicted structures show excellent agreement with experimental structures obtained from X-ray crystallography. [C4C1im][N(Tf)(Ac)] and [C4C1im][N(Ms)(TFA)] ILs have been synthesised and ion diffusion coefficients examined using pulsed field gradient stimulated echo NMR spectroscopy. Significantly increased diffusion was observed for the more flexible [N(Tf)(Ac)]− compared with the more rigid [N(Ms)(TFA)]− analogue. Furthermore, a pronounced impact on the fluidity was observed. The viscosity of the IL with the rigid anion was found to be twice as high as the viscosity of the IL with the flexible anion. The design concepts presented in this work will enable researchers in academia and industry to tailor anions to provide ILs with specific desired properties.
Clark R, Nawawi MA, Dobre A, et al., 2020, The effect of structural heterogeneity upon the microviscosity of ionic liquids, Chemical Science, Vol: 11, Pages: 6121-6133, ISSN: 2041-6520
The behaviour of two molecular rotors, one charged – 3,3′-diethylthiacarbocyanine iodide (Cy3) and one neutral – 8-[4-decyloxyphenyl]-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY-C10), have been studied in various ionic liquids. The fluorescent decay lifetime has been used to elucidate the structure of the immediate region around the rotor. The neutral BODIPY-C10 was found to prefer the non-polar alkyl chain environment, leading to two trends in the lifetime of the dye: one when it was fully partitioned into the non-polar domain, and one when it also sampled polar moieties. The positively charged Cy3 dye showed a complex relationship between the bulk viscosity of the ionic liquid and lifetime of the molecular rotor. This was attributed to a combination of polarity related spectral changes, changes in anion cages around the dye, and temperature dependent fluorescent lifetimes alongside the dependence of the rotor upon the viscosity.
Mann SK, Devgan MK, Franks WT, et al., 2020, MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 124, Pages: 4975-4988, ISSN: 1520-6106
Sillero L, Prado R, Welton T, et al., 2020, Energetic and environmental analysis of different techniques for biomolecules extractions, Chemical Engineering Transactions, Vol: 81, Pages: 631-636
There is an increase in the demand of natural and environmentally more sustainable products, for that the biorefinery is a very promising tool due to its capacity to develop more sustainable products. Biorefinery processes are being optimized to reduce the global energy consumption and environmental impact by increasing extraction yields. In this work, two intensification techniques, microwave-assisted extraction and ultrasound-assisted extraction, have been tested and their results have been compared with those obtained by the conventional method. The best results were obtained with microwave-assisted extraction. Another studied aspect was the selectivity of the solvent, for which three ionic liquids ([C4C1im][Br], [C4C1im][OAc] and [C4C1im][BF4]) and two deep eutectic solvents (Choline Chloride:Urea (1:2) and Choline Chloride: 1,4-butanediol (1:2)) were tested. The best extraction yield was obtained with Choline Chloride:Urea (1:2). The objective of this work was the evaluation of the impact of the processes in terms of energy consumption and solvents' toxicity, in addition to the determination of the extraction process performance. For this, an analysis of energy consumption was performed, with microwave assisted extraction having the lowest consumption. For the toxicity study different parameters were taken into account, concluding that deep eutectic solvents are a good option. In conclusion, the combination of microwave assisted extraction with deep eutectic solvents can be considered the most efficient extraction method.
Clark R, von Domaros M, McIntosh AJS, et al., 2019, Effect of an external electric field on the dynamics and intramolecular structures of ions in an ionic liquid, JOURNAL OF CHEMICAL PHYSICS, Vol: 151, ISSN: 0021-9606
Weber CC, Brooks NJ, Castiglione F, et al., 2019, On the structural origin of free volume in 1-alkyl-3-methylimidazolium ionic liquid mixtures: a SAXS and 129Xe NMR study., Physical Chemistry Chemical Physics, Vol: 21, Pages: 5999-6010, ISSN: 1463-9076
Ionic liquid (IL) mixtures enable the design of fluids with finely tuned structural and physicochemical properties for myriad applications. In order to rationally develop and design IL mixtures with the desired properties, a thorough understanding of the structural origins of their physicochemical properties and the thermodynamics of mixing needs to be developed. To elucidate the structural origins of the excess molar volume within IL mixtures containing ions with different alkyl chain lengths, 3 IL mixtures containing 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ILs have been explored in a joint small angle X-ray scattering (SAXS) and 129Xe NMR study. The apolar domains of the IL mixtures were shown to possess similar dimensions to the largest alkyl chain of the mixture with the size evolution determined by whether the shorter alkyl chain was able to interact with the apolar domain. 129Xe NMR results illustrated that the origin of excess molar volume in these mixtures was due to fluctuations within these apolar domains arising from alkyl chain mismatch, with the formation of a greater number of smaller voids within the IL structure. These results indicate that free volume effects for these types of mixtures can be predicted from simple considerations of IL structure and that the structural basis for the formation of excess molar volume in these mixtures is substantially different to IL mixtures formed of different types of ions.
Gehrke S, Reckien W, Palazzo I, et al., 2019, On the Carbene-Like Reactions of Imidazolium Acetate Ionic Liquids: Can Theory and Experiments Agree?, European Journal of Organic Chemistry, Vol: 2019, Pages: 504-511, ISSN: 1434-193X
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The N-heterocyclic carbene organocatalytic reactivity of the 1-ethyl-3-methylimidazolium acetate ionic liquid was investigated on the model reaction between this solvent and anisaldehyde. The formation of carbenes by a proton transfer from the cation to the anion was compared to a direct reaction mechanism, in which the proton transfer and the C–C bond formation between catalyst and substrate occurs in a single elementary step. Interestingly, the two reaction mechanisms show a much smaller difference in activation energies than those observed for analogous catalytic systems with neutral bases, showing that the mechanism might switch from one to the other at different temperatures or with different substrates. In this particular case, however, the direct reaction mechanism, avoiding free carbenes in the solution, is apparently more feasible. Based on the detailed analysis of this reaction path, the earlier contradictions between theory and experiments can be resolved, resulting in a consistent mechanistic picture for the related processes. Additionally, we show on the example of a platinum surface that introducing metal probes into the liquid may induce carbene-like reactions, as the formation of a strong coordinative bond between the carbene and a platinum atom at the surface is highly exothermic, shifting the acid-base equilibrium considerably.
Welton T, 2018, Editorial Overview: UN Sustainable Development Goals: How can sustainable/green chemistry contribute? There can be more than one approach, Current Opinion in Green and Sustainable Chemistry, Vol: 13, Pages: A7-A9, ISSN: 2452-2236
Welton T, 2018, Ionic liquids: a brief history., Biophysical Reviews, Vol: 10, Pages: 691-706, ISSN: 1867-2450
There is no doubt that ionic liquids have become a major subject of study for modern chemistry. We have become used to ever more publications in the field each year, although there is some evidence that this is beginning to plateau at approximately 3500 papers each year. They have been the subject of several major reviews and books, dealing with different applications and aspects of their behaviours. In this article, I will show a little of how interest in ionic liquids grew and developed.
Welton T, 2018, Ken Seddon-obituary., Biophys Rev, Vol: 10, ISSN: 1867-2450
Vincent S, Prado R, Kuzmina O, et al., 2018, Regenerated cellulose and willow lignin blends as potential renewable precursors for carbon fibers, ACS Sustainable Chemistry and Engineering, Vol: 6, Pages: 5903-5910, ISSN: 2168-0485
We report on the extraction of lignin from willow and its use to manufacture cellulose-lignin fibers as potential precursors for the manufacture of carbon fibers. The lignin from willow was extracted using triethylammonium hydrogen sulfate [Et3NH][HSO4]. The lignin extracted by this process was characterized by ATR-IR and elemental analysis, which indicated a high carbon yield. 1-Ethyl-3-methylimidazolium acetate [C2C1im][OAc] was then used as a common solvent to dissolve cellulose and lignin to manufacture lignin-cellulose fiber blends. The Young’s modulus of a 75:25 lignin/cellulose fiber was found to be 3.0 ± 0.5 GPa, which increased to 5.9 ± 0.6 GPa for a 25:75 lignin/cellulose blend. From a characterization of the surface morphology, using scanning electron microscopy (SEM) and atomic force microscopy (AFM), it was observed that higher lignin content in the fiber blend increased the surface roughness. FT-IR analysis confirmed the presence of aromatic groups related to lignin in the obtained fibers from the presence of peaks located at ∼1505 cm–1 and ∼1607 cm–1. The presence of lignin improves the thermal stability of the fiber blends by allowing them to degrade over a wider temperature range. The presence of lignin also improved the carbon yield during carbonization. Therefore, the lignin-cellulose fibers developed in this work can offer an excellent alternative to pure cellulose or lignin filaments.
Bastos JC, Carvalho SF, Welton T, et al., 2018, Design of task-specific fluorinated ionic liquids: nanosegregation versus hydrogen-bonding ability in aqueous solutions, Chemical Communications, Vol: 54, Pages: 3524-3527, ISSN: 1359-7345
We demonstrate that fluorinated ionic liquids reduce the impact of the addition of water upon the ionic liquid's H-bond acceptance ability. This is a key factor to obtain functionalized materials to be used e.g. in the dissolution of biomolecules, extraction processes or material engineering.
Clark R, Edel J, Kirchner B, et al., 2018, Ion diffusion in ionic liquids in electric fields, 255th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nexus of Food, Energy, and Water, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Holbrey J, Welton T, 2018, Obituary: Kenneth R. Seddon: 1950-2018, GREEN CHEMISTRY, Vol: 20, Pages: 776-776, ISSN: 1463-9262
Gehrke S, von Domaros M, Clark R, et al., 2018, Structure and lifetimes in ionic liquids and their mixtures, FARADAY DISCUSSIONS, Vol: 206, Pages: 219-245, ISSN: 1359-6640
Florindo C, McIntosh AJS, Welton T, et al., 2017, A closer look into deep eutectic solvents: exploring intermolecular interactions using solvatochromic probes., Physical Chemistry Chemical Physics, Vol: 20, Pages: 206-213, ISSN: 1463-9076
Deep eutectic solvents (DESs) constitute a new class of ionic solvents that has been developing at a fast pace in recent years. Since these solvents are commonly suggested as green alternatives to organic solvents, it is important to understand their physical properties. In particular, polarity plays an important role in solvation phenomena. In this work, the polarity of different families of DESs was studied through solvatochromic responses of UV-vis absorption probes. Kamlet-Taft α, β, π* and ETN parameters were evaluated using different solvatochromic probes, as 2,6-dichloro-4-(2,4,6-triphenyl-N-pyridino)-phenolate (Reichardt's betaine dye 33), 4-nitroaniline, and N,N-diethyl-4-nitroaniline for several families of DESs based on cholinium chloride, dl-menthol and a quaternary ammonium salt ([N4444]Cl). In addition, a study to understand the difference in polarity properties between DESs and the corresponding ILs, namely ILs based on cholinium cation and carboxylic acids as anions ([Ch][Lev], [Ch][Gly] and [Ch][Mal]), was carried out. The chemical structure of the hydrogen bond acceptor (HBA) in a DES clearly controls the dipolarity/polarizability afforded by the DES. Moreover, Kamlet-Taft parameters do not vary much within the family, but they differ among families based on different HBA, either for DESs containing salts ([Ch]Cl or [N4444]Cl) or neutral compounds (dl-menthol). A substitution of the HBD was also found to play an important role in solvatochromic probe behaviour for all the studied systems.
Kuzmina O, Bhardwaj J, Vincent SR, et al., 2017, Superbase ionic liquids for effective cellulose processing from dissolution to carbonisation, Green Chemistry, Vol: 19, Pages: 5949-5957, ISSN: 1463-9262
A range of superbase derived ionic liquids (SILs) was synthesised and characterised. Their ability to dissolve cellulose and the characteristics of the produced fibres were correlated to their specific structural and solvent properties. 17 ionic liquids (ILs) (including 9 novel) were analysed and six ILs were selected to produce fibres: 1-ethyl-3-methylimidazolium acetate [C2C1im][OAc], 1-ethyl-3-methylimidazolium diethyl phosphate [C2C1im][DEP] and the SILs 1-ethyl-1,8-diazabicyclo[5.4.0]undec-7-enium diethylphosphate [DBUEt][DEP], 1,8-diazabicyclo[5.4.0]undec-7-enium acetate [DBUH][OAc], 1,5-diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] and 1-ethyl-1,5-diazabicyclo[4.3.0]non-5-enium diethylphsophate [DBNEt][DEP]. The mechanical properties of these fibres were investigated. The obtained fibres were then carbonised to explore possible application as carbon fibre precursors. The fibres obtained using a mixture of 1,5-diazabicyclo[4.3.0]non-5-enium based SILs with acetate and hexanoate anions (9 : 1), [DBNH][OAc][Hex], showed a promising combination of strength, stiffness and strain at failure values for applications in textiles and fibre reinforcement in renewable composites. Using Raman spectroscopy it is demonstrated that these fibres exhibit a relatively high degree of structural order, with fewer defects than the other materials. On the other hand, analogous fibres based on imidazolium cation with acetate and hexanoate anions (9 : 1), [C2C1im][OAc][Hex] showed a decline in the quality of the produced fibres compared to the fibres produced from [C2C1im][OAc], [C2C1im][DEP] or [DBNH][OAc][Hex].
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