Imperial College London

Professor Tom Welton

Faculty of Natural SciencesDepartment of Chemistry

Professor of Sustainable Chemistry
 
 
 
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Contact

 

+44 (0)20 7594 5763t.welton Website

 
 
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Location

 

601AMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

240 results found

Koutsoukos S, Becker J, Dobre A, Fan Z, Othman F, Philippi F, Smith GJ, Welton Tet al., 2022, Synthesis of aprotic ionic liquids, Nature Reviews Methods Primers, Vol: 2

Ionic liquids (ILs) are typically a salt in the liquid state. They have been intensively investigated for many applications, including as solvents, electrolytes, catalysts, energy storage materials and lubricants, owing to their synthetic flexibility; there is a large number of different possible combinations of anions and cations, which can lead to ILs with very distinct properties. However, there is no standard methodology for the synthesis of ILs, with the quality of these being based solely on the internal experience of each research group. This Primer provides a guide to IL synthetic practices, outlining considerations when choosing the synthetic route as well as evaluating the advantages and disadvantages of each route. The Primer serves as a reference for both new and experienced researchers, to help determine whether the IL from a specific route will be suitable for their intended application, be it ultra-pure, fast or cheap.

Journal article

Palumbo O, Paolone A, Rauber D, Kay CWM, Philippi F, Welton Tet al., 2022, Mechanical spectroscopy study of ionic liquids with quaternary cations: Effect of conformational flexibility, Journal of Alloys and Compounds, Vol: 919, ISSN: 0925-8388

Mechanical spectroscopy measurements were performed on ionic liquids (ILs) with quaternary cations, either ammonium or phosphonium, and two anions, bis(trifluoromethanesulfonyl)imide ([NTf2]-) and bis(trifluoromethanesulfonyl)methanide ([CHTf2]-), which have almost the same molecular weight and degree of fluorination but exhibit different flexibility. Furthermore, the effect of multiple ether functionalization was studied by measuring the mechanical spectrum of [P(2O2)31][CHTf2]. The measured data evidence the occurrence of a relaxation process in the liquid phase of the ILs with flexible [NTf2]- anion and of [P(2O2)31][CHTf2], which is analyzed by means of a modified Debye model relating the peak to the ion hopping between non-equivalent configurations. The analysis confirms the involvement of nonequivalent anion configurations as well as their energy separation. For other ILs having rigid ions, instead, a fast dynamic at local level in the liquid phase is rarely observed since a partial transition to a solid state is favored. For these liquids, the measurements suggest the formation of aggregates which is suppressed by the multiple ether functionalization.

Journal article

Philippi F, Rauber D, Palumbo O, Goloviznina K, McDaniel J, Pugh D, Suarez S, Fraenza CC, Padua A, Kay CWM, Welton Tet al., 2022, Flexibility is the key to tuning the transport properties of fluorinated imide-based ionic liquids, CHEMICAL SCIENCE, ISSN: 2041-6520

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Guan Y, Clark R, Philippi F, Zhang X, Welton Tet al., 2022, How do external forces related to mass and charge affect the structures and dynamics of an ionic liquid?, JOURNAL OF CHEMICAL PHYSICS, Vol: 156, ISSN: 0021-9606

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Koutsoukos S, Philippi F, Rauber D, Pugh D, Kay C, Welton Tet al., 2022, Effect of the cation structure on the properties of homobaric imidazolium ionic liquids, Physical Chemistry Chemical Physics, Vol: 24, Pages: 6453-6468, ISSN: 1463-9076

In this work we investigate the structure–property relationships in a series of alkylimidazolium ionic liquids with almost identical molecular weight. Using a combination of theoretical calculations and experimental measurements, we have shown that re-arranging the alkyl side chain or adding functional groups results in quite distinct features in the resultant ILs. The synthesised ILs, although structurally very similar, cover a wide spectrum of properties ranging from highly fluid, glass forming liquids to high melting point crystalline salts. Theoretical ab initio calculations provide insight on minimum energy orientations for the cations, which then are compared to experimental X-ray crystallography measurements to extract information on hydrogen bonding and to verify our understanding of the studied structures. Molecular dynamics simulations of the simplest (core) ionic liquids are used in order to help us interpret our experimental results and understand better why methylation of C2 position of the imidazolium ring results in ILs with such different properties compared to their non-methylated analogues.

Journal article

Philippi F, Rauber D, Eliasen KL, Bouscharain N, Niss K, Kay CWM, Welton Tet al., 2022, Pressing matter: why are ionic liquids so viscous?, Chemical Science, Vol: 2022, ISSN: 2041-6520

We use an experimental approach to compare an ionic liquid with a molecular mimic, focusing on viscosities. Charge network and coulombic compaction contribute significantly to the high viscosity of ionic liquids; we discuss the implications on their design and optimisation.

Journal article

Harper JB, Kirchner B, Pavez P, Welton Tet al., 2021, Non-traditional solvent effects in organic reactions, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 26028-26029, ISSN: 1463-9076

Journal article

Sillero L, Prado R, Welton T, Labidi Jet al., 2021, Extraction of flavonoid compounds from bark using sustainable deep eutectic solvents, SUSTAINABLE CHEMISTRY AND PHARMACY, Vol: 24

Journal article

Rauber D, Philippi F, Kuttich B, Becker J, Kraus T, Hunt P, Welton T, Hempelmann R, Kay CWMet al., 2021, Curled cation structures accelerate the dynamics of ionic liquids, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 21042-21064, ISSN: 1463-9076

Journal article

Chan KLA, Shalygin AS, Martyanov ON, Welton T, Kazarian SGet al., 2021, High throughput study of ionic liquids in controlled environments with FTIR spectroscopic imaging, JOURNAL OF MOLECULAR LIQUIDS, Vol: 337, ISSN: 0167-7322

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Welton T, Welton T, 2021, Sustainability and international chemistry collaboration, NATIONAL SCIENCE REVIEW, Vol: 8, ISSN: 2095-5138

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Pontillo ARN, Koutsoukos S, Welton T, Detsi Aet 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

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Sillero L, Prado R, Welton T, Labidi Jet al., 2021, Energy and environmental analysis of flavonoids extraction from bark using alternative solvents, JOURNAL OF CLEANER PRODUCTION, Vol: 308, ISSN: 0959-6526

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Koutsoukos S, Philippi F, Malaret F, Welton Tet al., 2021, A review on machine learning algorithms for the ionic liquid chemical space, CHEMICAL SCIENCE, Vol: 12, Pages: 6820-6843, ISSN: 2041-6520

Journal article

Toda S, Clark R, Welton T, Shigeto Set 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

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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

Journal article

Bakis E, van den Bruinhorst A, Pison L, Palazzo I, Chang T, Kjellberg M, Weber CC, Gomes MC, Welton Tet al., 2021, Mixing divalent ionic liquids: effects of charge and side-chains, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 4624-4635, ISSN: 1463-9076

Journal article

Lemus J, Santiago R, Hospital-Benito D, Welton T, Hallett JP, Palomar Jet 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

Journal article

Welton T, 2020, A big difference in diversity, Education in Chemistry, Vol: 57, ISSN: 0013-1350

Journal article

Philippi F, Rauber D, Kuttich B, Kraus T, Kay CWM, Hempelmann R, Hunt PA, Welton Tet 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

Journal article

Philippi F, Pugh D, Rauber D, Welton T, Hunt PAet 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.

Journal article

Clark R, Nawawi MA, Dobre A, Pugh D, Liu Q, Ivanov AP, White AJP, Edel JB, Kuimova MK, McIntosh AJS, Welton Tet 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.

Journal article

Mann SK, Devgan MK, Franks WT, Huband S, Chan CL, Griffith J, Pugh D, Brooks NJ, Welton T, Pham TN, McQueen LL, Lewandowski JR, Brown SPet 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

Journal article

Sillero L, Prado R, Welton T, Labidi Jet 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.

Journal article

Clark R, von Domaros M, McIntosh AJS, Luzar A, Kirchner B, Welton Tet 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

Journal article

Weber CC, Brooks NJ, Castiglione F, Mauri M, Simonutti R, Mele A, Welton Tet 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.

Journal article

Gehrke S, Reckien W, Palazzo I, Welton T, Hollóczki Oet 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.

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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

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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.

Journal article

Welton T, 2018, Ken Seddon-obituary., Biophys Rev, Vol: 10, ISSN: 1867-2450

Journal article

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