Publications

Journal article

Eisermann J, Liang Y, Wright JJ, Clifford E, Wilton-Ely JDET, Kuimova M, Roessler Met al., 2024,

The effect of reactive oxygen species on respiratory complex I activity in liposomes

, Chemistry: A European Journal, Vol: 30, ISSN: 0947-6539

Respiratory complex I (R-CI) is an essential enzyme in the mitochondrial electron transport chain but also a major source of reactive oxygen species (ROS), which are implicated in neurodegenerative diseases and ageing. While the mechanism of ROS production by R-CI is well-established, the feedback of ROS on R-CI activity is poorly understood. Here, we perform EPR spectroscopy on R-CI incorporated in artificial membrane vesicles to reveal that ROS (particularly hydroxyl radicals) reduce R-CI activity by making the membrane more polar and by increasing its hydrogen bonding capability. Moreover, the mechanism that we have uncovered reveals that the feedback of ROS on R-CI activity via the membrane is transient and not permanent; lipid peroxidation is negligible for the levels of ROS generated under these conditions. Our successful use of modular proteoliposome systems in conjunction with EPR spectroscopy and other biophysical techniques is a powerful approach for investigating ROS effects on other membrane proteins.

Journal article

Jantan KA, Ekart G, McCarthy S, White AJP, Braddock DC, Serpe A, Wilton-Ely JDETet al., 2024,

Palladium complexes derived from waste as catalysts for C-H functionalisation and C-N bond formation

, Catalysts, Vol: 14, ISSN: 2073-4344

Three-way catalysts (TWCs) are widely used in vehicles to convert the exhaust emissions from internal combustion engines into less toxic pollutants. After around 8–10 years of use, the declining catalytic activity of TWCs causes them to need replacing, leading to the generation of substantial amounts of spent TWC material containing precious metals, including palladium. It has previously been reported that [NnBu4]2[Pd2I6] is obtained in high yield and purity from model TWC material using a simple, inexpensive and mild reaction based on tetrabutylammonium iodide in the presence of iodine. In this contribution, it is shown that, through a simple ligand exchange reaction, this dimeric recovery complex can be converted into PdI2(dppf) (dppf = 1,1′-bis(diphenylphosphino)ferrocene), which is a direct analogue of a commonly used catalyst, PdCl2(dppf). [NnBu4]2[Pd2I6] displayed high catalytic activity in the oxidative functionalisation of benzo[h]quinoline to 10-alkoxybenzo[h]quinoline and 8-methylquinoline to 8-(methoxymethyl)quinoline in the presence of an oxidant, PhI(OAc)2. Near-quantitative conversions to the desired product were obtained using a catalyst recovered from waste under milder conditions (50 °C, 1–2 mol% Pd loading) and shorter reaction times (2 h) than those typically used in the literature. The [NnBu4]2[Pd2I6] catalyst could also be recovered and re-used multiple times after the reaction, providing additional sustainability benefits. Both [NnBu4]2[Pd2I6] and PdI2(dppf) were also found to be active in Buchwald–Hartwig amination reactions, and their performance was optimised through a Design of Experiments (DoE) study. The optimised conditions for this waste-derived palladium catalyst (1–2 mol% Pd loading, 3–6 mol% of dppf) in a bioderived solvent, cyclopentyl methyl ether (CPME), offer a more sustainable approach to C-N bond formation than comparable amination protocols.

Journal article

Wilton-Ely J, 2023,

The Use of Recovered Metal Complexes in Catalysis

, JOHNSON MATTHEY TECHNOLOGY REVIEW, Vol: 67, Pages: 300-302, ISSN: 2056-5135

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Journal article

Eisermann J, Wright JJ, Wilton-Ely JDET, Hirst J, Roessler MMet al., 2023,

Using light scattering to assess how phospholipid-protein interactions affect complex I functionality in liposomes

, RSC Chemical Biology, Vol: 4, Pages: 386-398, ISSN: 2633-0679

Complex I is an essential membrane protein in respiration, oxidising NADH and reducing ubiquinone to contribute to the proton-motive force that powers ATP synthesis. Liposomes provide an attractive platform to investigate complex I in a phospholipid membrane with the native hydrophobic ubiquinone substrate and proton transport across the membrane, but without convoluting contributions from other proteins present in the native mitochondrial inner membrane. Here, we use dynamic and electrophoretic light scattering techniques (DLS and ELS) to show how physical parameters, in particular the zeta potential (ζ-potential), correlate strongly with the biochemical functionality of complex I-containing proteoliposomes. We find that cardiolipin plays a crucial role in the reconstitution and functioning of complex I and that, as a highly charged lipid, it acts as a sensitive reporter on the biochemical competence of proteoliposomes in ELS measurements. We show that the change in ζ-potential between liposomes and proteoliposomes correlates linearly with protein retention and catalytic oxidoreduction activity of complex I. These correlations are dependent on the presence of cardiolipin, but are otherwise independent of the liposome lipid composition. Moreover, changes in the ζ-potential are sensitive to the proton motive force established upon proton pumping by complex I, thereby constituting a complementary technique to established biochemical assays. ELS measurements may thus serve as a more widely useful tool to investigate membrane proteins in lipid systems, especially those that contain charged lipids.

Journal article

McCarthy S, Desaunay O, Lee Wei Jie A, Hassatzky M, White A, Deplano P, Braddock D, Serpe A, Wilton-Ely Jet al., 2022,

Homogeneous gold catalysis using complexes recovered from waste electronic equipment

, ACS Sustainable Chemistry and Engineering, Vol: 10, Pages: 15726-15734, ISSN: 2168-0485

Despite the greater awareness of elemental sustainability and the benefits of the circular economy concept, much waste electrical and electronic equipment (WEEE) is still destined for landfill. Effective methods for valorizing this waste within our society are therefore imperative. In this contribution, two gold(III) complexes obtained as recovery products from WEEE and their anion metathesis products were investigated as homogenous catalysts. These four recovery products were successfully applied as catalysts for the cyclization of propargylic amides and the condensation of acetylacetone with o-iodoaniline. Impressive activity was also observed in the gold-catalyzed reaction between electron-rich arenes (2-methylfuran, 1,3-dimethoxybenzene, and azulene) and α,β-unsaturated carbonyl compounds (methyl vinyl ketone and cyclohexenone). These recovered compounds were also shown to be effective catalysts for the oxidative cross-coupling reaction of aryl silanes and arenes. When employed as Lewis acid catalysts for carbonyl-containing substrates, the WEEE-derived gold complexes could also be recovered at the end of the reaction and reused without loss in catalytic activity, enhancing still further the sustainability of the process. This is the first direct application in homogeneous catalysis of gold recovery products sourced from e-waste.

Journal article

McCarthy S, Braddock D, Wilton-Ely J, 2021,

Strategies for sustainable palladium catalysis

, Coordination Chemistry Reviews, Vol: 442, Pages: 1-26, ISSN: 0010-8545

Palladium is established both as an indispensable metal in modern synthetic chemistry and as a key component in catalytic converters and electronic equipment. The unrelenting demand for this metal increases both the financial and environmental cost, through mining, of this metal, rendering consumption unsustainable in its current form. This review provides a critical survey of the main approaches being pursued to address this issue, including low-loading catalysis, recyclable catalysts and the use of palladium recovered from secondary sources. The literature discussed herein reveals that catalysts that operate at low loadings are an attractive, sustainable option for many transformations, even when compared to catalyst systems that can be reused multiple times. Both low-loading and reusable catalysts depend on a finite natural supply of palladium, making the development of catalysts based on metal recovered from end-of-life materials (urban mining) a promising field of research. The way in which low-loading is achieved in different catalyst designs influences the choice of reaction temperature and solvent, which has additional environmental implications. Such factors are discussed for a wide range of systems alongside reaction and substrate scope, supported by extensive supplementary information. The survey aims to provide an insight into the relative merits of the approaches being explored and how the field of palladiumbased catalysis might progress towards more sustainable use of this critical metal.

Journal article

McCarthy S, Lee Wei Jie A, Braddock D, Serpe A, Wilton-Ely Jet al., 2021,

From waste to green applications: the use of recovered gold and palladium in catalysis

, Molecules, Vol: 26, ISSN: 1420-3049

The direct use in catalysis of precious metal recovery products from industrial and consumer waste is a very promising recent area of investigation. It represents a more sustainable, environmentally benign, and profitable way of managing the low abundance of precious metals, as well as encouraging new ways of exploiting their catalytic properties. This review demonstrates the feasibility and sustainability of this innovative approach, inspired by circular economy models, and aims to stimulate further research and industrial processes based on the valorisation of secondary resources of these raw materials. The overview of the use of recovered gold and palladium in catalytic processes will be complemented by critical appraisal of the recovery and reuse approaches that have been proposed.

Journal article

Al Ghatta A, Zhou X, Casarano G, Wilton-Ely J, Hallett Jet al., 2021,

Characterization and valorization of humins produced by HMF degradation in ionic liquids: a valuable carbonaceous material for antimony removal

, ACS Sustainable Chemistry and Engineering, Vol: 9, Pages: 2212-2223, ISSN: 2168-0485

The processing of biomass in ionic liquids has demonstrated many benefits compared to organic solvents. This includes the maximization of 5-hydroxymethylfurfural (HMF) yield from sugars through the suppression of byproducts, such as formic acid and levulinic acid. Inefficiencies still exist due to the low stability of HMF at high temperature, leading to side reactions which ultimately result in the undesirable formation of humins. Valorization of this polymeric side product is thus needed to improve the economics of the biorefinery and could lead to humins being viewed as valuable materials for various applications. However, a much better understanding is needed of how humins form from HMF in the various ionic liquids proposed for the biorefinery. In this contribution, humin formation is probed by a range of analytical techniques, including FT-IR, SEM, solid-state 13C NMR, MS, GPC, and XPS analyses. This reveals that the structure and morphology of the humins formed does not resemble those reported in the literature and that the material displays a number of unique aspects. The hydrogen bonding proprieties of the ionic liquids employed exert a strong influence on the chemical functionality of the humins, and this is used to demonstrate their potential as functional materials. To demonstrate this, the humins produced in various ionic liquid environments are applied to metal extraction and compared with commercial activated carbon. This reveals that humins are superior for the extraction of antimony ions from wastewater, showing promise as an adsorbent additive for water purification.

Journal article

Al Ghatta A, Wilton-Ely J, Hallett J, 2021,

From sugars to FDCA: A techno-economic assessment using a design concept based on solvent selection and carbon dioxide emissions

, Green Chemistry, Vol: 23, Pages: 1716-1733, ISSN: 1463-9262

The synthesis of the molecule 2,5-furandicarboxylic acid (FDCA) from sugars is key to unlocking the potential for the replacement of the oil derivative PET (polyethylene terephthalate) by polyethylene furanoate (PEF). Although much research and investment has been dedicated to the synthesis of FDCA, there remains limited commercial activity in this area due to the challenges related to the stability and isolation of the FDCA precursor, 5-hydroxymethylfurfural (HMF). High yields of HMF can be obtained from fructose at high loadings in water–organic solvent mixtures (methyl isobutyl ketone, MIBK; γ-valerolactone, GVL), dimethyl sulfoxide (DMSO) or ionic liquids. Each of these approaches suffers from various drawbacks in terms of catalyst development, product separation and environmental impact. It is therefore necessary to understand which of these processes has the potential for scale-up, while ensuring low environmental impact and a competitive selling price. In this study, a process simulation (rather than a life cycle assessment) was performed to evaluate the associated emissions and selling price of FDCA based on its production using different solvents. It was determined that the cost and CO2 emissions associated with the isolation of HMF undermine the economic and environmental viability of the transformation of sugars to FDCA. In contrast, a two-step, one-pot reaction represents an ideal solution to reduce both cost and environmental impact, making FDCA competitive with terephthalic acid (the corresponding precursor for PET). The choice of solvent and the process were then evaluated and ranked based on safety, CO2 emissions, selling price and state of development though a scoring methodology. A system based on a water/GVL mixture is closer to commercial applicability but the process is limited by extensive formation of humins, which reduces the overall yield of the process, increasing the minimum selling price of FDCA. Using DMSO or ionic liquids mi

Journal article

Shi X, Perry H, Wilton-Ely J, 2021,

Strategies for the functionalisation of gold nanorods to reduce toxicity and aid clinical translation

, Nanotheranostics, Vol: 5, Pages: 155-165, ISSN: 2206-7418

Gold nanorods (GNRs) show great promise as photothermal therapy agents due to their remarkable ability to convert light into heat. In most cases, gold nanorods are synthesised via a seed-mediated method assisted by surfactants. However, the toxicity of these surfactants, principally cetrimonium ions, has prevented GNRs from being used more widely in vivo. To address this issue, various detoxification and functionalisation approaches have been proposed in recent years to replace or cover surfactant coatings on the gold surface. In this short review, the advantages and limitations of each approach are examined in the context of the recent progress made towards the design of GNRs suitable for use in the body.

Journal article

Guinart A, Perry HL, Wilton-Ely JDET, Tetley TDet al., 2020,

Gold nanomaterials in the management of lung cancer

, Emerging Topics in Life Sciences, Vol: 4, Pages: 627-643, ISSN: 2397-8554

Lung cancer (LC) is one of the most deadly cancers worldwide, with very low survival rates, mainly due to poor management, which has barely changed in recent years. Nanomedicines, especially gold nanomaterials, with their unique and size-dependent properties offer a potential solution to many challenges in the field. The versatility afforded by the shape, size, charge and surface chemistry of gold nanostructures allows them to be adapted for many applications in the diagnosis, treatment and imaging of LC. In this review, a survey of the most recent advances in the field is presented with an emphasis on the optical properties of gold nanoscale materials and their use in cancer management. Gold nanoparticle toxicology has also been a focus of interest for many years but the studies have also sometimes arrived at contradictory conclusions. To enable extrapolation and facilitate the development of medicines based on gold nanomaterials, it must be assumed that each design will have its own unique characteristics that require evaluation before translation to the clinic. Advances in the understanding and recognition of the molecular signatures of LC have aided the development of personalised medicines. Tailoring the treatment to each case should, ideally increase the survival outcomes as well as reduce medical costs. This review seeks to present the potential of gold nanomaterials in LC management and to provide a unified view, which will be of interest to those in the field as well as researchers considering entering this highly important area of research.

Journal article

Robson JA, Kubánková M, Bond T, Hendley RA, White AJP, Kuimova MK, WiltonEly JDETet al., 2020,

Simultaneous detection of carbon monoxide and viscosity changes in cells

, Angewandte Chemie, Vol: 132, Pages: 21615-21619, ISSN: 0044-8249

A new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via fluorescence lifetime imaging microscopy (FLIM) while also monitoring CO levels. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells.

Journal article

Robson J, Kubankova M, Bond T, Hendley R, White A, Kuimova M, Wilton-Ely Jet al., 2020,

Simultaneous detection of carbon monoxide and viscosity changes in cells

, Angewandte Chemie International Edition, Vol: 59, Pages: 21431-21435, ISSN: 1433-7851

A new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via Fluorescence Lifetime Imaging Microscopy (FLIM) in conjunction with measuring CO. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells.

Journal article

Perry H, Yoon I, Chabloz N, Molisso S, Stasiuk G, Botnar R, Wilton-Ely Jet al., 2020,

Metallostar assemblies based on dithiocarbamates for use as MRI contrast agents

, Inorganic Chemistry, Vol: 59, Pages: 10813-10823, ISSN: 0020-1669

Two different octadentate gadolinium chelates based on DO3A and DOTAGA chelates (hydration number q = 1) have been used to prepare a series of bi-, tri-, and tetrametallic d–f mixed-metal complexes. The piperazine-based dithiocarbamate linker ensures that rotation of the gadolinium chelates is restricted, leading to enhanced relaxivity (r1) values, which increase with the overall mass and number of gadolinium units. The r1 value (at 10 MHz, 25 °C) per gadolinium unit rises from 5.0 mM–1 s–1 for the Gd-DO3A-NH2 monogadolinium chelate to 9.2 mM–1 s–1 in a trigadolinium complex with a ruthenium(III) core. Using a 1.5 T clinical scanner operating at 63.87 MHz (25 °C), an 86% increase in the relaxivity per gadolinium unit is observed for this multimetallic compound compared to clinically approved Dotarem. The gadolinium complexes based on the DOTAGA chelate also performed well at 63.87 MHz, with a relaxivity value of 9.5 mM–1 s–1 per gadolinium unit being observed for the trigadolinium d–f mixed-metal complex with a ruthenium(III) core. The versatility of dithiocarbamate coordination chemistry thus provides access to a wide range of d–f hybrids with potential for use as high-performance MRI contrast agents.

Journal article

Perry H, Botnar R, Wilton-Ely J, 2020,

Gold nanomaterials functionalised with gadolinium chelates and their application in multimodal imaging and therapy

, Chemical Communications, Vol: 56, Pages: 4037-4046, ISSN: 1359-7345

Over the last decade, much work has been dedicated to improving the performance of gadolinium-based magnetic resonance imaging (MRI) contrast agents by tethering them to biocompatible gold nanoparticles. The enhancement in performance (measured in terms of ‘relaxivity’) stems from the restriction in motion experienced by the gadolinium chelates on being attached to the gold nanoparticle surface. More recently, the unique properties of gold nanoparticles have been exploited to create very promising tools for multimodal imaging and MRI-guided therapies. This review addresses the progress made in the design of gadolinium-functionalised gold nanoparticles for use in MRI, multimodal imaging and theranostics. It also seeks to connect the chemical properties of these assemblies with potential application in the clinic.

Journal article

Chabloz N, Perry H, Yoon I-C, Coulson A, White A, Stasiuk G, Botnar R, Wilton-Ely Jet al., 2020,

Combined magnetic resonance imaging and photodynamic therapy using polyfunctionalised nanoparticles bearing robust gadolinium surface units

, Chemistry – A European Journal, Vol: 26, Pages: 4552-4566, ISSN: 0947-6539

A robust dithiocarbamate tether allows novel gadolinium units based on DOTAGA (q = 1) to be attached to the surface of gold nanoparticles (2.6 ‐ 4.1 nm diameter) along with functional units offering biocompatibility, targeting and photodynamic therapy. A dramatic increase in relaxivity (r1) per Gd unit from 5.01 mM−1 s−1 in unbound form to 31.68 mM−1 s−1 (10 MHz, 37 °C) is observed when immobilised on the surface due to restricted rotation and enhanced rigidity of the Gd complex on the nanoparticle surface. The single‐step synthetic route provides a straightforward and versatile way of preparing multifunctional gold nanoparticles, including examples with conjugated zinc‐tetraphenylporphyrin photosensitizers. The lack of toxicity of these materials (MTT assays) is transformed on irradiation of HeLa cells for 30 minutes (PDT), leading to 75% cell death. In addition to passive targeting, the inclusion of units capable of actively targeting overexpressed folate receptors illustrates the potential of these assemblies as targeted theranostic agents.

Journal article

Al Ghatta A, Wilton-Ely JDET, Hallett JP, 2020,

Efficient formation of 2,5-diformylfuran (DFF) in ionic liquids at high substrate loadings and low oxygen pressure with separation through sublimation

, ACS Sustainable Chemistry & Engineering, Vol: 8, Pages: 2462-2471, ISSN: 2168-0485

The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) using oxygen (1 atm) with a TEMPO and CuCl catalyst system is investigated using a range of imidazolium-based ionic liquids (ILs) and various bases at different HMF substrate loadings (10-50%). This represents the first example of HMF to DFF conversion in ionic liquid media under homogeneous catalysis conditions, revealing dramatic differences in performance between the ILs. In the non-coordinating, hydrophobic ionic liquid, [bmim][NTf2], 90% DFF yield is obtained at 5 mol% catalyst loading after 6 hours at 80 °C at a very high 40% HMF loading. Increasing the temperature to 100 °C leads to a lower yield, attributed to loss of volatile TEMPO from the reaction medium. A system using TEMPO and pyridine immobilized within the ionic liquid [bmim][NTf2] results in selective conversion of HMF to high purity DFF. It also allows the DFF formed to be isolated by sublimation in 81% yield before a further cycle is performed. Subsequent catalyst deactivation is probed by X-ray photoelectron spectroscopy (XPS). Synthesis from fructose in a two-step process achieves a 55% isolated DFF yield. This approach overcomes significant drawbacks previously reported for this transformation, such as solvent toxicity, separation and purification problems as well as the need for high oxygen pressures. Further oxidation of HMF with this system leads to a 62% yield of 5-formyl-2-furancarboxylic acid (FFCA). The separation of this compound can be achieved by sublimation of DFF followed by solvent extraction.

Journal article

García-Calvo J, Robson J, Torroba T, Wilton-Ely Jet al., 2019,

Synthesis and application of ruthenium(II) alkenyl complexes with perylene fluorophores for the detection of toxic vapours and gases

, Chemistry – A European Journal, Vol: 25, Pages: 14214-14222, ISSN: 0947-6539

A series of new ruthenium(II) vinyl complexes has been prepared incorporating perylenemonoimide (PMI) units. This fluorogenic moiety was functionalised with terminal alkyne or pyridyl groups, allowing attachment to the metal either as a vinyl ligand or through the pyridyl nitrogen. The inherent low solubility of the perylene compounds was improved through the design of poly‐PEGylated (PEG = polyethylene glycol) units bearing a terminal alkyne or a pyridyl group. By absorbing the compounds on silica, vapours and gases could be detected in the solid state. The reaction of the complexes [Ru(CH=CH‐PerIm)Cl(CO)(py‐3PEG)(PPh3)2] and [Ru(CH=CH‐3PEG)Cl(CO)(py‐PerIm)(PPh3)2] with carbon monoxide, isonitrile or cyanide was found to result in modulation of the fluorescence behaviour. The complexes were observed to display solvatochromic effects and the interaction of the complexes with a wide range of other species was also studied. The study suggests that such complexes have potential for the detection of gases or vapours that are toxic to humans.

Journal article

Al Ghatta A, Wilton-Ely J, Hallett J, 2019,

Rapid, high‐yield fructose dehydration to HMF in mixtures of water and the non‐coordinating Ionic Liquid [bmim][OTf]

, ChemSusChem, Vol: 12, Pages: 4452-4460, ISSN: 1864-5631

The non‐coordinating ionic liquid [bmim][OTf] is an effective and versatile solvent for the high‐yield dehydration of fructose to the platform chemical HMF over short reaction times. In contrast to literature reports, which report low yields for this transformation in ionic liquids (ILs) with non‐coordinating anions, this contribution reveals that the water content is an essential parameter for an efficient reaction in ILs. Achieving the optimum amount of water can increase the yield dramatically by regulating the acidity of the catalyst and partially suppressing the side reaction caused by self‐condensation of HMF. Using acid catalysis in [bmim][OTf] with 3.5% water content, yields above 80% can be achieved at 100 °C in only 10 minutes, even at high (14%) fructose loading. These results suggest that [bmim][OTf] represents a superior medium for solvent extraction of HMF compared to halide‐based ILs, allowing the option of isolation or further valorisation of the HMF formed.

Journal article

Al Ghatta A, Wilton-Ely JDET, Hallett JP, 2019,

Strategies for the separation of the furanic compounds HMF, DFF, FFCA and FDCA from Ionic liquids

, ACS Sustainable Chemistry & Engineering, Vol: 7, Pages: 16483-16492, ISSN: 2168-0485

The catalytic upgrading of sugar derivatives into valuable building blocks represents an extremely important challenge intrinsic to the attempts to establish a green economy. However, the significance of separation and purification are often relegated to a marginal role or overlooked completely despite this aspect being critical for potential scale up. It is well established that the synthesis of 5-hydroxymethylfurfural (HMF) from sugars in ionic liquid media is a valuable, sustainable and high-yielding chemical pathway, but product separation has always remained an unresolved issue. In this contribution, the separation of HMF and three of its derivatives, 2,5-diformylfuran (DFF), 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) from ionic liquids is analyzed. Various ionic liquids are screened in order to obtain an optimal separation process. The extraction of HMF is studied from the hydrophobic methyltrioctylammonium ionic liquids with water, obtaining a favorable partition coefficient for the aqueous phase. In contrast, its derivatives, DFF, FFCA and FDCA, can be easily separated by phase separation. DFF retains its sublimation attributes in the ionic liquid and can be readily separated in quantitative yields in high purity. This behavior is observed in ionic liquids but is not achievable in common organic solvents. FDCA and FFCA are separated by water addition and precipitation. It is found that less water is required for the precipitation of these compounds compared to dimethylsulfoxide (DMSO), which is a frequently employed reaction medium for their generation. The energy balance for regeneration of the ionic liquid after water addition is estimated using the enterprise ionic liquids database ILUAM. This study provides a set of solvent design guidelines for the selective synthesis, isolation and purification of these compounds in ionic liquids, aiding future reaction design.

Journal article

Chabloz N, Wenzel M, Perry H, Yoon I, Molisso S, Stasiuk G, Elson D, Cass A, Wilton-Ely Jet al., 2019,

Polyfunctionalised nanoparticles bearing robust gadolinium surface units for high relaxivity performance in MRI

, Chemistry - A European Journal, Vol: 25, Pages: 10895-10906, ISSN: 0947-6539

The first example of an octadentate gadolinium unit based on DO3A (hydration number q = 1) with a dithiocarbamate tether has been designed and attached to the surface of gold nanoparticles (around 4.4 nm in diameter). In addition to the superior robustness of this attachment, the restricted rotation of the Gd complex on the nanoparticle surface leads to a dramatic increase in relaxivity (r1) from 4.0 mM‐1 s‐1 in unbound form to 34.3 mM‐1 s‐1 (at 10 MHz, 37 °C) and 22 ± 2 mM‐1s‐1 (at 63.87 MHz, 25 °C) when immobilised on the surface. The ‘one‐pot’ synthetic route provides a straightforward and versatile way of preparing a range of multifunctional gold nanoparticles. The incorporation of additional surface units improving biocompatibility (PEG and thioglucose units) and targeting (folic acid) lead to little detrimental effect on the high relaxivity observed for these non‐toxic multifunctional materials. In addition to the passive targeting attributed to gold nanoparticles, the inclusion of a unit capable of targeting the folate receptors overexpressed by cancer cells, such as HeLa cells, illustrates the potential of these assemblies.

Journal article

Anuar Jantan K, Chan KW, Melis L, White A, Marchio L, Deplano P, Serpe A, Wilton-Ely JDETet al., 2019,

From recovered palladium to molecular and nanoscale catalysts

, ACS Sustainable Chemistry & Engineering, Vol: 7, Pages: 12389-12398, ISSN: 2168-0485

[PdI2(Me2dazdt)] is obtained from palladium powder via a 100% atom economical Pd(0) leaching reaction using Me2dazdt (N,N’-dimethyl-perhydrodiazepine-2,3-dithione) and iodine. This complex is a versatile starting point for ligand exchange reactions with (di)phosphines, yielding trans-[PdI2(PPh3)2] and [PdI2(dppe)] (dppe = 1,2-bis(diphenylphosphino)ethane). Further reaction with dithiocarbamates provides compounds of the form [Pd(DTC)(L)n]+ (DTC = dithiocarbamate; L = PPh3, n = 2; L = dppe, n = 1), which are highly active catalysts for regio- and chemo-selective C-H bond activation reactions. Using DTC ligands with trimethoxysily-terminated tethers, the palladium(II) units can be attached to the surface of core-shell, silica-coated Fe3O4 nanoparticles. Once tethered, these units formed the catalytically-active component of a recyclable, quasi-heterogeneous, Pd(II)-based catalytic system based on recovered palladium, illustrating the proposed circular model strategy. These investigations contribute to key steps in this process, such as efficient, atom-economical recovery, chemoselectivity of ligand substitution reactions, demonstration of catalytic activity and the potential for immobilization of catalytic surface units derived from recovered metal.

Journal article

Mognon L, Richardson S, Agonigi G, Bond T, Marchetti F, Wilton-Ely Jet al., 2019,

Heterotrimetallic complexes of iron and ruthenium based on vinyliminium dithiocarboxylate ligands

, Journal of Organometallic Chemistry, Vol: 886, Pages: 9-12, ISSN: 0022-328X

The diiron vinyliminium compounds [Fe2{μ-η1:η3-C(R2) = C(H)C=N(Me)R1}(μ-CO)(CO)(Cp)2]OSO2CF3 (R1 = Xyl = 2,6-C6H3Me2, R2 = Me; R1 = Me, R2 = CO2Me) provide a versatile entry point for many subsequent transformations, such as their reaction with carbon disulfide to provide zwitterionic dithiocarboxylate products. These compounds react with the coordinatively-unsaturated ruthenium vinyl precursors [Ru(CH=CHR3)Cl(CO)(PPh3)2] (R3 = C6H4Me-4, 1-Pyrenyl) to yield heterotrimetallic Fe2Ru compounds, exhibiting vinyl moieties at both iron and ruthenium centres. The emission associated with the pyrenyl unit is enhanced in the diiron vinyliminium ruthenium pyrenyl complex compared to the diethyldithiocarbamate analogue.

Journal article

Jantan KA, McArdle J, Mognon L, Fiorini V, Wilkinson LA, White AJP, Stagni S, Long NJ, Wilton-Ely Jet al., 2019,

Heteromultimetallic compounds based on polyfunctional carboxylate linkers

, New Journal of Chemistry, Vol: 43, Pages: 3199-3207, ISSN: 1144-0546

A series of homo- and hetero-nuclear, bi- and trimetallic compounds are accessible using polyfunctional linkers with carboxylic acid and alkynyl or pyridyl donor combinations. This versatile approach affords reaction at a specific donor site in each case, to accommodate both ruthenium(II) or osmium(II) units and also rhenium and gold centres. Due to the orientation of the nitrogen donors of the bipyridyl moiety in 2,2′-bipyridine-4,4′-dicarboxylic acid, the metal addition must be performed in a certain sequence due to steric considerations. One example was investigated crystallographically to add to the spectroscopic and analytical characterisation performed for all complexes. Photophysical investigations reveal the effect of incorporating second or third row transition metal centres. This approach was expanded through the use of a linker bearing both carboxylic acid and alkynyl functionalities, 1,1′-ethynylferrocene carboxylic acid. This allows initial coordination of the carboxylate donors to be followed by the formation of either an acetylide or a vinyl bridge to another metal, providing access to heterotrimetallic (FeRuOs and FeRuAu) compounds as well as a heteroheptametallic Fe3Ru2Au2 example. Preliminary electrochemical studies were performed on the latter compound.

Journal article

Toscani A, Marín-Hernández C, Robson J, Chua E, Dingwall P, White A, Sancenón F, de la Torre C, Martínez-Máñez R, Wilton-Ely Jet al., 2019,

Highly sensitive and selective molecular probes for chromo-fluorogenic sensing of carbon monoxide in air, aqueous solution and cells

, Chemistry - A European Journal, Vol: 25, Pages: 2069-2081, ISSN: 0947-6539

Optical sensing offers a low‐cost and effective means to sense carbon monoxide in air and in solution. This contribution reports the synthesis of a new series of vinyl complexes [Ru(CH=CHR)Cl(CO)(TBTD)(PPh3)2] (R = aryl, TBTD = 5‐(3‐thienyl)‐2,1,3‐benzothiadiazole) and shows them to be highly sensitive and selective probes for carbon monoxide in both solution and air. Depending on the vinyl substituent, chromogenic and fluorogenic responses signalled the presence of this invisible, odourless, tasteless and toxic gas. Adsorbing the complexes on silica produced colorimetric probes for the ‘naked eye’ detection of CO in the gas phase with a limit of detection as low as 8 ppm in some cases, while the release of the TBTD fluorophore allowed detection at much lower concentrations through the fluorescence response. Structural data were obtained by single crystal X‐ray diffraction techniques, while the photophysical behaviour was explored computationally using TD‐DFT experiments. The systems were also shown to be selective for CO over all other gases tested, including water vapour and common organic solvents. By introducing a poly(ethylene)glycol chain to the vinyl functionality, water compatibility was achieved and these non‐cytotoxic complexes were employed in the sensing of CO in HeLa cells, offering a simple and rapid system for sensing this gasotransmitter in this challenging medium.

Journal article

de la Torre C, Toscani A, Marin-Hernandez C, Robson J, Terencio M, White A, Alcaraz M, Wilton-Ely JD, Martinez-Manez R, Sancenon Fet al., 2017,

Ex vivo tracking of endogenous CO with a ruthenium(II) complex

, Journal of the American Chemical Society, Vol: 139, Pages: 18484-18487, ISSN: 1520-5126

A two-photon fluorescent probe based on a ruthenium(II) vinyl complex is capable of selectively detecting carbon monoxide in cells and ex vivo using mice with a subcutaneous air pouch as a model for inflammation. This probe combines highly selective and sensitive ex vivo detection of endogenous CO in a realistic model with facile, inexpensive synthesis, and displays many advantages over the widely used palladium-based systems.

Journal article

Wilton-Ely JD, white A, Jantan K, Chan K, Kwok C, Serpe A, Marchio L, Deplano Pet al., 2017,

From recovered metal waste to high-performance palladium catalysts

, Green Chemistry, Vol: 19, Pages: 5846-5853, ISSN: 1463-9262

The catalytic activity of a series of neutral and cationic, homo- and heteroleptic, mono- and bimetallic palladium(II) compounds based on dithiocarbamate and dithiooxamide S,S-donor ligands is described. High activity was observed in the regio- and chemo-selective C–H functionalization of benzo[h]quinoline to 10-alkoxybenzo[h]quinoline and 8-methylquinoline to 8-(methoxymethyl)quinoline in the presence of the oxidant PhI(OAc)2. The best performance was found for [Pd(Me2dazdt)2]I6 (Me2dazdt = N,N′-dimethyl-perhydrodiazepine-2,3-dithione), [PdI2(Me2dazdt)] and [Pd(Cy2DTO)2]I8 (Cy2DTO = N,N′-dicyclohexyl-dithiooxamide) which are all obtained directly as products of sustainable Pd-metal leaching processes used to recover palladium from scrap metal. These compounds provided almost quantitative yields under milder conditions (50 °C, 1–3 mol% Pd loading) and much shorter reaction times (1–3 h) than reported previously. These results illustrate how the complexes obtained from the selective and sustainable recovery of Pd from automotive heterogeneous Three Way Catalysts (TWC) can be employed directly in homogeneous catalysis, avoiding further metal recovery steps and valorising the metal complex itself in a ‘circular economy’ model.

Journal article

Rasekh M, Ahmad Z, Cross R, Hernandez-Gil J, Wilton-Ely JDET, Miller PWet al., 2017,

Facile Preparation of Drug-Loaded Tristearin Encapsulated Superparamagnetic Iron Oxide Nanoparticles Using Coaxial Electrospray Processing

, MOLECULAR PHARMACEUTICS, Vol: 14, Pages: 2010-2023, ISSN: 1543-8384

Naturally occurring polymers are promising biocompatible materials that have many applications for emerging therapies, drug delivery systems, and diagnostic agents. The handling and processing of such materials still constitutes a major challenge, which can limit the full exploitation of their properties. This study explores an ambient environment processing technique: coaxial electrospray (CO-ES) to encapsulate genistein (an isoflavonoid and model drug), superparamagnetic iron oxide nanoparticles (SPIONs, 10–15 nm), and a fluorophore (BODIPY) into a layered (triglyceride tristearin shell) particulate system, with a view to constructing a theranostic agent. Mode mapping of CO-ES led to an optimized atomization engineering window for stable jetting, leading to encapsulation of SPIONs within particles of diameter 0.65–1.2 μm and drug encapsulation efficiencies of around 92%. Electron microscopy was used to image the encapsulated SPIONs and confirm core–shell triglyceride encapsulation in addition to further physicochemical characterization (AFM, FTIR, DSC, and TGA). Cell viability assays (MTT, HeLa cells) were used to determine optimal SPION loaded particles (∼1 mg/mL), while in vitro release profile experiments (PBS, pH = 7.4) demonstrate a triphasic release profile. Further cell studies confirmed cell uptake and internalization at selected time points (t = 1, 2, and 4 h). The results suggest potential for using the CO-ES technique as an efficient way to encapsulate SPIONs together with sensitive drugs for the development of multimodal particles that have potential application for combined imaging and therapy.

Journal article

Robson JA, Gonzàlez de Rivera F, Jantan KA, Wenzel MN, White AJ, Rossell O, Wilton-Ely JDet al., 2016,

Bifunctional chalcogen linkers for the stepwise generation of multimetallic assemblies and functionalized nanoparticles

, Inorganic Chemistry, Vol: 55, Pages: 12982-12996, ISSN: 1520-510X

The disulfide ligand (SC6H4CO2H-4)2 acts as a simple but versatile linker for a range of group 8 transition metals through reaction of the oxygen donors. This leads to a range of homobimetallic ruthenium and osmium alkenyl compounds, [{M(CH═CHR)(CO)(PPh3)2(O2CC6H4S-4)}2] (M = Ru, Os; R = C6H4Me-4). Additional metal-based functionality can be added through the use of precursors incorporating rhenium bipyridine units (R = (bpy)ReCl(CO)3). The more robust diphosphine ligands in [{Ru(dppm)2(O2CC6H4S-4)}2](2+) (dppm = diphenylphosphinomethane) allow reduction of the disulfide bond with sodium borohydride to yield the thiol complex [Ru(O2CC6H4SH-4)(dppm)2](+). This complex reacts with [AuCl(PPh3)] to afford the bimetallic compound [Ru(dppm)2(O2CC6H4S-4)Au(PPh3)](+). However, an improved route to the same and related heterobimetallic compounds is provided by the reaction of cis-[RuCl2(dppm)2] with [Au(SC6H4CO2H-4)(L)] (L = PPh3, PCy3, PMe3, IDip) in the presence of base and NH4PF6 (IDip = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). The heterotrimetallic compound [Au(SC6H4CO2Ru(dppm)2)2](+) is accessible through the reaction of the homoleptic gold(I) dithiolate [Au(SC6H4CO2H-4)2]PPN (PPN = bis(triphenylphosphine)iminium) with cis-[RuCl2(dppm)2]. Without departure from the same methodology, greater complexity can be incorporated into the system to provide the penta- and heptametallic assemblies [(dppf){AuSC6H4CO2Ru(dppm)2}2](2+) and [(dppf){AuSC6H4CO2Os(CH═CH-bpyReCl(CO)3)(CO)(PPh3)2}2]. The same stepwise approach provides the dinuclear organometallic complexes [(L)Au(SC6H4CO2-4)M(CH═CHC6H4Me-4)(CO)(PPh3)2] (M = Ru, Os; L = PPh3, IDip). Complexes containing three metals from different groups of the periodic table [(L)Au(SC6H4CO2-4)M{CH═CH-bpyReCl(CO)3}(CO)(PPh3)2] (M = Ru, Os) can also be prepared, with one ruthenium example (L = PPh3) being structurally characterized. In order to illustrate the versatility of this approach, the synthesis and characterization (IR and

Journal article

Toscani A, Jantan KA, Hena JB, Robson JA, Parmenter EJ, Fiorini V, White AJ, Stagni S, Wilton-Ely JDet al., 2016,

The stepwise generation of multimetallic complexes based on a vinylbipyridine linkage and their photophysical properties

, Dalton Transactions, Vol: 46, Pages: 5558-5570, ISSN: 1477-9226

The versatile rhenium complex [ReCl(CO)3(bpyC[triple bond, length as m-dash]CH)] (HC[triple bond, length as m-dash]Cbpy = 5-ethynyl-2,2'-bipyridine) is used to generate a series of bimetallic complexes through the hydrometallation of [MHCl(CO)(BTD)(PPh3)2] (M = Ru, Os; BTD = 2,1,3-benzothiadiazole). The ruthenium complex [Ru{CH[double bond, length as m-dash]CH-bpyReCl(CO)3}Cl(BTD)(CO)(PPh3)2] was characterised structurally. Ligand exchange reactions with bifunctional linkers bearing oxygen and sulfur donors provide access to tetra- and pentametallic complexes such as [{M{CH[double bond, length as m-dash]CH-bpyReCl(CO)3}(CO)(PPh3)2}2(S2CNC4H8NCS2)] and Fe[C5H4CO2M{CH[double bond, length as m-dash]CH-bpyReCl(CO)3}(CO)(PPh3)2]2. The effect of the group 8 metal on the photophysical properties of the rhenium centre was investigated using the complexes [Ru{CH[double bond, length as m-dash]CH-bpyReCl(CO)3}Cl(BTD)(CO)(PPh3)2] and [M{CH[double bond, length as m-dash]CH-bpyReCl(CO)3}{S2P(OEt)2}(CO)(PPh3)2] (M = Ru, Os). This revealed the quenching of the rhenium-based emission in favour of weak radiative processes based on the Ru and Os centres. The potential for exploiting this effect is illustrated by the reaction of [Ru{CH[double bond, length as m-dash]CH-bpyReCl(CO)3}Cl(CO)(BTD)(PPh3)2] with carbon monoxide, which results in a 5-fold fluorescence enhancement in the dicarbonyl product, [Ru{CH[double bond, length as m-dash]CH-bpyReCl(CO)3}Cl(CO)2(PPh3)2], as the quenching effect is disrupted.

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The effect of reactive oxygen species on respiratory complex I activity in liposomes

Palladium complexes derived from waste as catalysts for C-H functionalisation and C-N bond formation

The Use of Recovered Metal Complexes in Catalysis

Using light scattering to assess how phospholipid-protein interactions affect complex I functionality in liposomes

Homogeneous gold catalysis using complexes recovered from waste electronic equipment

Strategies for sustainable palladium catalysis

From waste to green applications: the use of recovered gold and palladium in catalysis

Characterization and valorization of humins produced by HMF degradation in ionic liquids: a valuable carbonaceous material for antimony removal

From sugars to FDCA: A techno-economic assessment using a design concept based on solvent selection and carbon dioxide emissions

Strategies for the functionalisation of gold nanorods to reduce toxicity and aid clinical translation

Gold nanomaterials in the management of lung cancer

Simultaneous detection of carbon monoxide and viscosity changes in cells

Simultaneous detection of carbon monoxide and viscosity changes in cells

Metallostar assemblies based on dithiocarbamates for use as MRI contrast agents

Gold nanomaterials functionalised with gadolinium chelates and their application in multimodal imaging and therapy

Combined magnetic resonance imaging and photodynamic therapy using polyfunctionalised nanoparticles bearing robust gadolinium surface units

Efficient formation of 2,5-diformylfuran (DFF) in ionic liquids at high substrate loadings and low oxygen pressure with separation through sublimation

Synthesis and application of ruthenium(II) alkenyl complexes with perylene fluorophores for the detection of toxic vapours and gases

Rapid, high‐yield fructose dehydration to HMF in mixtures of water and the non‐coordinating Ionic Liquid [bmim][OTf]

Strategies for the separation of the furanic compounds HMF, DFF, FFCA and FDCA from Ionic liquids

Polyfunctionalised nanoparticles bearing robust gadolinium surface units for high relaxivity performance in MRI

From recovered palladium to molecular and nanoscale catalysts

Heterotrimetallic complexes of iron and ruthenium based on vinyliminium dithiocarboxylate ligands

Heteromultimetallic compounds based on polyfunctional carboxylate linkers

Highly sensitive and selective molecular probes for chromo-fluorogenic sensing of carbon monoxide in air, aqueous solution and cells

Ex vivo tracking of endogenous CO with a ruthenium(II) complex

From recovered metal waste to high-performance palladium catalysts

Facile Preparation of Drug-Loaded Tristearin Encapsulated Superparamagnetic Iron Oxide Nanoparticles Using Coaxial Electrospray Processing

Bifunctional chalcogen linkers for the stepwise generation of multimetallic assemblies and functionalized nanoparticles

The stepwise generation of multimetallic complexes based on a vinylbipyridine linkage and their photophysical properties

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