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Wilton-Ely J, 2006, Dinuclear ruthenium and osmium compounds with metal-metal bonds, Comprehensive Organometallic Chemistry III, Editor(s): Crabtree, Mingos, Elsevier, Pages:647-716, ISBN:978-0080445908

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  • 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
    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 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.

  • Journal article
    Eminov S, Filippousi P, Brandt A, Wilton-Ely J, Hallett Jet al., 2016,

    Direct catalytic conversion of cellulose to 5-hydroxymethylfurfural using ionic liquids

    , Inorganics, Vol: 4, ISSN: 2304-6740

    Cellulose is the single largest component of lignocellulosic biomass and is an attractive feedstock for a wide variety of renewable platform chemicals and biofuels, providing an alternative to petrochemicals and petrofuels. This potential is currently limited by the existing methods of transforming this poorly soluble polymer into useful chemical building blocks, such as 5-hydroxymethylfurfural (HMF). Ionic liquids have been used successfully to separate cellulose from the other components of lignocellulosic biomass and so the use of the same medium for the challenging transformation of cellulose into HMF would be highly attractive for the development of the biorefinery concept. In this report, ionic liquids based on 1-butyl-3-methylimidazolium cations [C4C1im]+ with Lewis basic (X = Cl−) and Brønsted acidic (X = HSO4−) anions were used to investigate the direct catalytic transformation of cellulose to HMF. Variables probed included the composition of the ionic liquid medium, the metal catalyst, and the reaction conditions (temperature, substrate concentration). Lowering the cellulose loading and optimising the temperature achieved a 58% HMF yield after only one hour at 150 °C using a 7 mol % loading of the CrCl3 catalyst. This compares favourably with current literature procedures requiring much longer reactions times or approaches that are difficult to scale such as microwave irradiation.

  • Journal article
    Eminov S, Brandt A, Wilton-Ely JD, Hallett JPet al., 2016,

    The Highly Selective and Near-Quantitative Conversion of Glucose to 5-Hydroxymethylfurfural Using Ionic Liquids

    , PLOS One, Vol: 11, ISSN: 1932-6203

    A number of ionic liquids have been shown to be excellent solvents for lignocellulosic biomass processing, and some of these are particularly effective in the production of the versatile chemical building block 5-hydroxymethylfurfural (HMF). In this study, the production of HMF from the simple sugar glucose in ionic liquid media is discussed. Several aspects of the selective catalytic formation of HMF from glucose have been elucidated using metal halide salts in two distinct ionic liquids, 1-butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium hydrogen sulfate as well as mixtures of these, revealing key features for accelerating the desired reaction and suppressing byproduct formation. The choice of ionic liquid anion is revealed to be of particular importance, with low HMF yields in the case of hydrogen sulfate-based salts, which are reported to be effective for HMF production from fructose. The most successful system investigated in this study led to almost quantitative conversion of glucose to HMF (90% in only 30 minutes using 7 mol% catalyst loading at 120°C) in a system which is selective for the desired product, has low energy intensity and is environmentally benign.

  • Journal article
    Collinson J-M, Wilton-Ely JDET, Diez-Gonzalez S, 2016,

    Functionalised [(NHC)Pd(allyl)Cl] complexes: Synthesis, immobilisation and application in cross-coupling and dehalogenation reactions

    , Catalysis Communications, Vol: 87, Pages: 78-81, ISSN: 1566-7367

    A novel NHC–palladium(II) (NHC = N-heterocyclic carbene) complex and itsimmobilised version have been prepared and fully characterised. Optimisation studies led to goodcatalytic activities in Suzuki-Miyaura cross coupling and chloroarene dehalogenation reactions.Furthermore, the unexpected palladium-mediated transfer hydrogenation of a carbonyl compound isreported.

  • Journal article
    Wilton-Ely JD, Toscani A, Marin-Hernandez C, Sancenon F, Martinez-Manez Ret al., 2016,

    Chromo-fluorogenic probes for carbon monoxide detection

    , Chemical Communications, Vol: 52, Pages: 5902-5911, ISSN: 1364-548X

    The sensing of carbon monoxide (CO) using electrochemical cells or semiconducting metal oxides has led to inexpensive alarms for the home and workplace. It is now recognised that chronic exposure to low levels of CO also poses a significant health risk. It is perhaps surprising therefore that the CO is used in cell-signalling pathways and plays a growing role in therapy. However, the selective monitoring of low levels of CO remains challenging, and it is this area that has benefited from the development of probes which give a colour or fluorescence response. This feature article covers the design of chromo-fluorogenic probes and their application to CO sensing in air, solution and in cells.

  • Journal article
    Wilton-Ely JD, Toscani A, Brown N, Dingwall P, White A, Marin-Hernandez C, Moragues M, Sancenon F, Martinez-Manez Ret al., 2015,

    Ruthenium(II) and Osmium(II) vinyl complexes as highly sensitive and selective chromogenic and fluorogenic probes for the sensing of carbon monoxide in air

    , Chemistry - A European Journal, Vol: 21, Pages: 14529-14538, ISSN: 0947-6539

    The detection of carbon monoxide in solution and air has been achieved using simple, inexpensive systems based on the vinyl complexes [M(CH[DOUBLE BOND]CHR)Cl(CO)(BTD)(PPh3)2] (R=aryl, BTD=2,1,3-benzothiadiazole). Depending on the nature of the vinyl group, chromogenic and fluorogenic responses signalled the presence of this odourless, tasteless, invisible, and toxic gas. Solutions of the complexes in CHCl3 underwent rapid change between easily differentiated colours when exposed to air samples containing CO. More significantly, the adsorption of the complexes on silica produced colorimetric probes for the naked-eye detection of CO in the gas phase. Structural data for key species before and after the addition of CO were obtained by means of single X-ray diffraction studies. In all cases, the ruthenium and osmium vinyl complexes studied showed a highly selective response to CO with exceptionally low detection limits. Naked-eye detection of CO at concentrations as low as 5 ppb in air was achieved with the onset of toxic levels (i.e., 100 ppm), thus resulting in a remarkably clear colour change. Moreover, complexes bearing pyrenyl, naphthyl, and phenanthrenyl moieties were fluorescent, and greater sensitivities were achieved (through turn-on emission fluorescence) in the presence of CO both in solution and air. This behaviour was explored computationally using time-dependent density functional theory (TDDFT) experiments. In addition, the systems were shown to be selective for CO over all other gases tested, including water vapour and common organic solvents. Supporting the metal complexes on cellulose strips for use in an existing optoelectronic device allows numerical readings for the CO concentration to be obtained and provision of an alarm system.

  • Journal article
    Sherwood R, Gonzàlez de Rivera F, Wan JH, Zhang Q, White AJ, Rossell O, Hogarth G, Wilton-Ely JDet al., 2015,

    Multimetallic complexes based on a diphosphine-dithiocarbamate "janus" ligand.

    , Inorganic Chemistry, Vol: 54, Pages: 4222-4230, ISSN: 1520-510X

    The HCl salt of the aminodiphosphine ligand HN(CH2CH2PPh2)2 reacts with [M(CO)4(pip)2] (M = Mo, W; pip = piperidine) to yield [M{κ(2)-HN(CH2CH2PPh2)2}(CO)4]. The molybdenum analogue readily loses a carbonyl ligand to form [Mo{κ(3)-HN(CH2CH2PPh2)2}(CO)3], which was structurally characterized. The same ligand backbone is used to form the new bifunctional ligand, KS2CN(CH2CH2PPh2)2, which reacts with nickel and cobalt precursors to yield [Ni{S2CN(CH2CH2PPh2)2}2] and [Co{S2CN(CH2CH2PPh2)2}3]. Addition of [AuCl(tht)] (tht = tetrahydrothiophene) to [Ni{S2CN(CH2CH2PPh2)2}2] leads to formation of the pentametallic complex, [Ni{S2CN(CH2CH2PPh2AuCl)2}2]. In contrast, addition of [PdCl2(py)2] (py = pyridine) to [Ni{S2CN(CH2CH2PPh2)2}2] does not lead to a trimetallic complex but instead yields the transmetalated cyclic compound [Pd{S2CN(CH2CH2PPh2)2}]2, which was structurally characterized. The same product is obtained directly from [PdCl2(py)2] and KS2CN(CH2CH2PPh2)2. In contrast, the same reaction with [PtCl2(NCPh)2] yields the oligomer, [Pt{S2CN(CH2CH2PPh2)2}]n. Reaction of KS2CN(CH2CH2PPh2)2 with cis-[RuCl2(dppm)2] provides [Ru{S2CN(CH2CH2PPh2)2}(dppm)2](+), which reacts with [AuCl(tht)] to yield [Ru{S2CN(CH2CH2PPh2AuCl)2}(dppm)2](+). Addition of [M(CO)4(pip)2] (M = Mo, W) to the same precursor leads to formation of the bimetallic compounds [(dppm)2Ru{S2CN(CH2CH2PPh2)2}M(CO)4](+), while treatment with [ReCl(CO)5] yields [(dppm)2Ru{S2CN(CH2CH2PPh2)2}ReCl(CO)3](+). Reaction of KS2CN(CH2CH2PPh2)2 with [Os(CH═CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole) provides [Os(CH═CHC6H4Me-4){S2CN(CH2CH2PPh2)2}(CO)(PPh3)2], but reaction with the analogous ruthenium precursor fails to yield a clean product.

  • Journal article
    Toscani A, Helioevaara EK, Hena JB, White AJP, Wilton-Ely JDETet al., 2015,

    Multimetallic Alkenyl Complexes Bearing Macrocyclic Dithiocarbamate Ligands

    , Organometallics, Vol: 34, Pages: 494-505, ISSN: 1520-6041
  • Journal article
    Hurtubise VL, McArdle JM, Naeem S, Toscani A, White AJP, Long NJ, Wilton-Ely JDETet al., 2014,

    Multimetallic Complexes and Functionalized Nanoparticles Based on Unsymmetrical Dithiocarbamate Ligands with Allyl and Propargyl Functionality

    , INORGANIC CHEMISTRY, Vol: 53, Pages: 11740-11748, ISSN: 0020-1669
  • Journal article
    Moragues ME, Toscani A, Sancenon F, Martinez-Manez R, White AJP, Wilton-Ely JDETet al., 2014,

    A Chromo-fluorogenic synthetic "Canary" for CO detection based on a Pyrenylvinyl Ruthenium(II) complex

    , Journal of the American Chemical Society, Vol: 136, Pages: 11930-11933, ISSN: 0002-7863

    The chromo-fluorogenic detection of carbon monoxide in air has been achieved using a simple, inexpensive system based on ruthenium(II). This probe shows exceptional sensitivity and selectivity in its sensing behavior in the solid state. A color response visible to the naked eye is observed at 5 ppb of CO, and a remarkably clear color change occurs from orange to yellow at the onset of toxic CO concentrations (100 ppm) in air. Even greater sensitivity (1 ppb) can be achieved through a substantial increase in turn-on emission fluorescence in the presence of carbon monoxide, both in air and in solution. No response is observed with other gases including water vapor. Immobilization of the probe on a cellulose strip allows the system to be applied in its current form in a simple optoelectronic device to give a numerical reading and/or alarm.

  • Journal article
    Cecchini MP, Turek VA, Demetriadou A, Britovsek G, Welton T, Kornyshev AA, Wilton-Ely JDET, Edel JBet al., 2014,

    Heavy Metal Sensing Using Self-Assembled Nanoparticles at a Liquid–Liquid Interface

    , Advanced Optical Materials

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