Portrait of Dr Christopher Serpell

Dr Christopher Serpell

Senior Lecturer in Chemistry
Head of the Functional Materials Group

About

Dr Chris Serpell completed his undergraduate studies at the University of Oxford, graduating in 2005 with a first class MChem after a final year project with Professor Paul Beer. After a year teaching physical and analytical chemistry at the University of Brighton, he returned to Paul Beer’s group for DPhil studies (co-funded and supervised by Johnson Matthey) which encompassed anion co-ordination, halogen bonding, crystallography, and metal nanoparticles. Chris was a finalist in the Reaxys PhD Prize, and was awarded EPSRC PhD+ funding for extension projects. 

In 2011 he moved to McGill University in Montreal as a Tomlinson, and then Banting Fellow in Professor Hanadi Sleiman’s group, and worked at the interface of DNA, peptide, and polymer nanotechnologies. Chris returned to the UK in 2014, taking up a Marie Curie Experienced Researcher Fellowship in Professor Ben Davis’s group at Oxford as part of an Innovative Training Network developing the use of filled carbon nanotubes in medicine and biology. Chris was appointed Lecturer in Chemistry at the University of Kent in July 2015 and is a member of the Functional Materials Group in the School of Physical Sciences.

Research interests

The Serpell Group works at the interfaces of biomolecular and synthetic supramolecular chemistry, and nanotechnology. Their overarching aim is to exploit the breadth and depth of these fields, forging new links and generating new chemical structures, functions, and technologies.

Sequence-defined polymers

The secrets of life are written in the sequences of polymers: nucleic acids and proteins. Among their attributes, these biopolymers are capable of storing vast quantities of information, catalysing reactions to the diffusion limit with absolute selectivity, creating materials of exceptional strength and resilience, and imparting microscopic and macroscopic motion. In all these cases, it is supramolecular chemistry – non-covalent interactions such as hydrogen bonding, π-stacking, electrostatics, and the hydrophobic effect – that acts as to translate monomer sequence into function and activity.
Dr Serpell and his colleagues are recapitulating these concepts using synthetic motifs by applying solid-phase synthesis in a new way. The non-natural sequence-defined polymers they are generating are capable of programmed folding, molecular recognition, and biological function. They use the automated phosphoramidite synthesis used typically for DNA to produce highly modified oligonucleotides, DNA-peptide hybrids, and entirely non-nucleosidic sequence-defined polymers, for fundamentals of self-assembly, and applications in therapy, sensing, and catalysis via discovery of sequences with high affinity. The Serpell Group collaborates with industrial aptamer scientists and a number of groups in the Kent School of Biosciences on this topic.

Drug delivery: Polymer-as-payload

Nanotechnology holds immense promise for improving the efficacy of known drugs by providing temporal and spatial control over release of the active compound. However, most systems that do this contain far more polymer than drug, and this is a problem when a high local dose is needed – for example, in the use of non-steroidal anti-inflammatory drugs for chemoprevention of certain cancers. 

The Serpell Group is making polymers out of the drugs themselves, such that the polymers can be formulated into targeted nanoparticles, which will then degrade to release the drug at a controllable rate, at the proper therapeutic site (eg the cancer). A recent example of this is the creation of degradable polymer nanoparticles built out of salicylic acid. The group is expanding this approach to other drugs, and developing collaborations with Malaysia to use therapeutic phytochemicals in this regard.

Biomolecular manipulation

Despite being able to perform tasks well beyond the current capabilities of synthetic chemistry, biomolecules are not magic. Proteins, peptides, lipids, sugars, and nucleic acids all display chemical ‘handles’ which can be used to manipulate their behaviour. Chris and his team are exploiting covalent and supramolecular motifs to provide new ways to detect and purify biomolecules, and translate their unique properties to novel functional materials. A recent example of this is the use of gold nanoparticles as adjuncts in electrophoretic analysis of sulphurous biomolecules.

Publications

Article

  • Young, A. et al. (2019). One-step synthesis and XPS investigations of chiral NHC–Au(0)/Au(i) nanoparticles. Nanoscale [Online] 11:8327-8333. Available at: https://doi.org/10.1039/C9NR00905A.
    Although N-heterocyclic carbenes (NHCs) have been demonstrated as suitable ligands for the stabilisation of gold nanoparticles (AuNPs) through a variety of methods, the manner in which such AuNPs form is yet to be fully elucidated. We report a simple and fast one-step synthesis of uniform chiral (L/D)-histidin-2-ylidene stabilised gold nanoparticles using the organometallic Au(I) complex as a well defined starting material. The resulting nanoparticles have an average size of 2.35 ± 0.43 nm for the L analog whereas an average size of 2.25 ± 0.39 nm was found for the D analog. X-ray photoelectron spectroscopy analyses reveal the presence of Au(I) and Au(0) in all NHC stabilised AuNPs. In contrast, measured X-ray photoelectron spectra of dodecanethiol protected gold nanoparticles showed only the presence of a Au(0) species. This observation leads us to postulate that AuNPs synthesised from organometallic NHC–Au(I) complexes exhibit a monolayer of Au(I) surrounding a Au(0) core. This work highlights the importance of synthetic method choice for NHC-stabilized AuNPs, as this could determine Au oxidation states and resulting AuNP properties such as catalytic activities and stabilities.
  • Appukutti, N. and Serpell, C. (2018). High-definition polyphosphoesters: between nucleic acids and plastics. Polymer Chemistry [Online] 9:2210-2216. Available at: https://doi.org/10.1039/C8PY00251G.
    Polyphosphoesters are common to both genetics and cutting-edge polymer science. This review seeks to reframe current conceptions of the boundaries of nucleic acid and polymer chemistry, showing that vital ‘stepping stones’ are now in place, allowing us to make a journey through chemical space between DNA and the synthetic polyphosphoesters. These liminal classes of macromolecule address vital questions about sequence control in polymers, single polymer chain folding, programmed self-assembly, nanoscale photophysics, and chemical data storage. In taking this path, we will impinge upon biochemistry, medicine, photophysics, supramolecular chemistry, nanotechnology, information technology and materials science. The synthetic methods we already have in hand have only just begun to show their promise in all these fields.
  • Akkad, M. and Serpell, C. (2018). Degradable Polymers and Nanoparticles Built from Salicylic Acid. Macromolecular Rapid Communications [Online] 39:1800182. Available at: https://doi.org/10.1002/marc.201800182.
    As more evidence emerges supporting the possibility that non-steroidal anti-inflammatory drugs, especially aspirin (acetyl salicylic acid), might have a role in the prevention and management in certain types of cancer, there have been several attempts to fabricate salicylic acid-based polymers that can be employed in the targeted therapy of tumours. The primary disadvantage so far has been in use of non-therapeutic polymeric backbones that constitute the majority of the therapeutic particle’s size. The focus of this research is the creation of a biodegradable polymer consisting only of salicylic acid, and its use as the main building block in targeted nanotherapeutics that would consequently provide both high local dose and sustained release of the active moiety. In this work, we demonstrate the synthesis and degradation of polysalicylates, and modulation of their size and hydrolytic stability through formation of nanostructures.
  • Davis, B. and Serpell, C. (2017). Nanotechnology and Biotechnology: Two Way Traffic. Editorial Overview: Nanotechnology and biotechnology: Two way traffic [Online] 46:vi-viii. Available at: http://dx.doi.org/10.1016/j.copbio.2017.06.002.
    Editorial overview for special issue of Current Opinion in Biotechnology on Nanobiotechnology
  • Young, A. et al. (2017). Optically active histidin-2-ylidene stabilised gold nanoparticles. Chemical Communications [Online] 53:12426-12429. Available at: http://dx.doi.org/10.1039/C7CC07602A.
    Drawing from the natural amino acid chiral pool, L and D histidines were utilized as chiral NHC ligands in the synthesis of NHC-stabilized chiroptical gold nanoparticles. Centrifugal size selection afforded monodisperse gold nanoparticles which display mirrored signals in CD spectroscopy.
  • Serpell, C., Kostarelos, K. and Davis, B. (2016). Can Carbon Nanotubes Deliver on their Promise in Biology? Harnessing Unique Properties for Unparalleled Applications. ACS Central Science [Online] 2:190-200. Available at: http://dx.doi.org/10.1021/acscentsci.6b00005.
  • Avakyan, N. et al. (2016). Reprogramming the assembly of unmodified DNA with a small molecule. Nature Chemistry [Online]. Available at: http://dx.doi.org/10.1038/nchem.2451.
    The ability of DNA to store and encode information arises from base pairing of the four-letter nucleobase code to form a double helix. Expanding this DNA ‘alphabet’ by synthetic incorporation of new bases can introduce new functionalities and enable the formation of novel nucleic acid structures. However, reprogramming the self-assembly of existing nucleobases presents an alternative route to expand the structural space and functionality of nucleic acids. Here we report the discovery that a small molecule, cyanuric acid, with three thymine-like faces reprogrammes the assembly of unmodified poly(adenine) (poly(A)) into stable, long and abundant fibres with a unique internal structure. Poly(A) DNA, RNA and peptide nucleic acid all form these assemblies. Our studies are consistent with the association of adenine and cyanuric acid units into a hexameric rosette, which brings together poly(A) triplexes with a subsequent cooperative polymerization. Fundamentally, this study shows that small hydrogen-bonding molecules can be used to induce the assembly of nucleic acids in water, which leads to new structures from inexpensive and readily available materials.
  • Chidchob, P. et al. (2016). Synergy of Two Assembly Languages in DNA Nanostructures: Self-Assembly of Sequence-Defined Polymers on DNA Cages. Journal of the American Chemical Society [Online] 138:4416-4425. Available at: http://pubs.acs.org/doi/abs/10.1021/jacs.5b12953.
    DNA base-pairing is the central interaction in DNA assembly. However, this simple four-letter (A-T and
    G-C) language makes it difficult to create complex structures without using a large number of DNA
    strands of different sequences. Inspired by protein folding, we introduce hydrophobic interactions to
    expand the assembly language of DNA nanotechnology. To achieve this, DNA cages of different
    geometries are combined with sequence-defined polymers containing long alkyl and oligoethylene glycol
    repeat units. Anisotropic decoration of hydrophobic polymers on one face of the cage leads to
    hydrophobically-driven formation of quantized aggregates of DNA cages, where polymer length
    determines the cage aggregation number. Hydrophobic chains decorated on both faces of the cage can
    undergo an intra-scaffold ‘handshake’ to generate DNA-micelle cages, which have increased structural
    stability and assembly cooperativity, and can encapsulate small molecules. The polymer sequence order
    can control the interaction between hydrophobic blocks, leading to unprecedented ‘doughnut-shaped’
    DNA cage-ring structures. We thus demonstrate that new structural and functional modes in DNA
    nanostructures can emerge from the synergy of two interactions, providing an attractive approach to
    develop protein-inspired assembly modules in DNA nanotechnology.
  • Serpell, C. et al. (2016). Carbon nanotubes allow capture of krypton, barium and lead for multichannel biological X-ray fluorescence imaging. Nature Communications [Online] 7:13118. Available at: http://dx.doi.org/10.1038/ncomms13118.
    The desire to study biology in situ has been aided by many imaging techniques. Among these, X-ray fluorescence (XRF) mapping permits observation of elemental distributions in a multichannel manner. However, XRF imaging is underused, in part, because of the difficulty in interpreting maps without an underlying cellular ‘blueprint’; this could be supplied using contrast agents. Carbon nanotubes (CNTs) can be filled with a wide range of inorganic materials, and thus can be used as ‘contrast agents’ if biologically absent elements are encapsulated. Here we show that sealed single-walled CNTs filled with lead, barium and even krypton can be produced, and externally decorated with peptides to provide affinity for sub-cellular targets. The agents are able to highlight specific organelles in multiplexed XRF mapping, and are, in principle, a general and versatile tool for this, and other modes of biological imaging.
  • Edwardson, T. et al. (2016). Transfer of molecular recognition information from DNA nanostructures to gold nanoparticles. Nature Chemistry [Online] 8:162-170. Available at: http://dx.doi.org/10.1038/NCHEM.2420.
    DNA nanotechnology offers unparalleled precision and programmability for the bottom-up organization of materials. This approach relies on pre-assembling a DNA scaffold, typically containing hundreds of different strands, and using it to position functional components. A particularly attractive strategy is to employ DNA nanostructures not as permanent
    scaffolds, but as transient, reusable templates to transfer essential information to other materials. To our knowledge, this approach, akin to top-down lithography, has not been examined. Here we report a molecular printing strategy that chemically transfers a discrete pattern of DNA strands from a three-dimensional DNA structure to a gold nanoparticle.
    We show that the particles inherit the DNA sequence configuration encoded in the parent template with high fidelity. This provides control over the number of DNA strands and their relative placement, directionality and sequence asymmetry. Importantly, the nanoparticles produced exhibit the site-specific addressability of DNA nanostructures, and are promising components for energy, information and biomedical applications.
  • Castor, K. et al. (2015). Cyclometalated Iridium(III) Imidazole Phenanthroline Complexes as Luminescent and Electrochemiluminescent G-Quadruplex DNA Binders. Inorganic Chemistry [Online] 54:6958-6967. Available at: http://doi.org/10.1021/acs.inorgchem.5b00921.
    Six cyclometalated iridium(III) phenanthroimidazole complexes with different modifications to the imidazole phenanthroline ligand exhibit enhanced luminescence when bound to guanine (G-) quadruplex DNA sequences. The complexes bind with low micromolar affinity to human telomeric and c-myc sequences in a 1:1 complex:quadruplex stoichiometry. Due to the luminescence enhancement upon binding to G-quadruplex DNA, the complexes can be used as selective quadruplex indicators. In addition, the electrogenerated chemiluminescence of all complexes increases in the presence of specific G-quadruplex sequences, demonstrating potential for the development of an ECL-based G-quadruplex assay.
  • Langton, M., Serpell, C. and Beer, P. (2015). Anion Recognition in Water: Recent Advances from a Supramolecular and Macromolecular Perspective. Angewandte Chemie International Edition [Online]:n/a-n/a. Available at: http://doi.org/10.1002/anie.201506589.
    The recognition of anions in water remains a key challenge in modern supramolecular chemistry, and is essential if proposed applications in biological, medical, and environmental arenas that typically require aqueous conditions are to be achieved. However, synthetic anion receptors that operate in water have, in general, been the exception rather than the norm to date. Nevertheless, a significant step change towards routinely conducting anion recognition in water has been achieved in the past few years, and this Review highlights these approaches, with particular focus on controlling and using the hydrophobic effect, as well as more exotic interactions such as C?H hydrogen bonding and halogen bonding. We also look beyond the field of small-molecule recognition into the macromolecular domain, covering recent advances in anion recognition based on biomolecules, polymers, and nanoparticles.
  • Serpell, C. et al. (2014). Nucleobase peptide amphiphiles. Materials Horizons [Online] 1:348-354. Available at: http://doi.org/10.1039/C3MH00154G.
    A new class of peptide materials is introduced, integrating orthogonal aspects of peptide, nucleoside, and amphiphile chemistry. In solution, species such as rod-like or helical micelles are formed, which can lead to nanoribbons under lateral or longitudinal hierarchical growth regimes. Gelation of a wide range of solvents can be induced, including water and aqueous buffer, providing new avenues for nucleobase-specific electrophoresis, oligonucleotide delivery and bioactive cell growth media.
  • Serpell, C. et al. (2014). Precision polymers and 3D DNA nanostructures: Emergent assemblies from new parameter space. Journal of the American Chemical Society [Online] 136:15767-15774. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84908691501&partnerID=40&md5=bdd6606564dedccf666e93f71cac08cf.
    Polymer self-assembly and DNA nanotechnology have both proved to be powerful nanoscale techniques. To date, most attempts to merge the fields have been limited to placing linear DNA segments within a polydisperse block copolymer. Here we show that, by using hydrophobic polymers of a precisely predetermined length conjugated to DNA strands, and addressable 3D DNA prisms, we are able to effect the formation of unprecedented monodisperse quantized superstructures. The structure and properties of larger micelles-of-prisms were probed in depth, revealing their ability to participate in controlled release of their constituent nanostructures, and template light-harvesting energy transfer cascades, mediated through both the addressability of DNA and the controlled aggregation of the polymers. © 2014 American Chemical Society.
  • Edwardson, T. et al. (2014). An efficient and modular route to sequence-defined polymers appended to DNA. Angewandte Chemie - International Edition [Online] 53:4567-4571. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84899541371&partnerID=40&md5=e8ebdbe46f9f1bb1daf33e12093ce747.
    Inspired by biological polymers, sequence-controlled synthetic polymers are highly promising materials that integrate the robustness of synthetic systems with the information-derived activity of biological counterparts. Polymer-biopolymer conjugates are often targeted to achieve this union; however, their synthesis remains challenging. We report a stepwise solid-phase approach for the generation of completely monodisperse and sequence-defined DNA-polymer conjugates using readily available reagents. These polymeric modifications to DNA display self-assembly and encapsulation behavior - as evidenced by HPLC, dynamic light scattering, and fluorescence studies - which is highly dependent on sequence order. The method is general and has the potential to make DNA-polymer conjugates and sequence-defined polymers widely available. Bilingual: A stepwise solid-phase synthesis approach provides easy access to sequence-controlled polymers attached to DNA. Polymers with the same molecular composition but different monomer patterns exhibit different amphiphilic self-assembly. The DNA component still retains base-pairing fidelity, and thus one molecule "speaks" two orthogonal and programmable assembly languages. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • White, N., Serpell, C. and Beer, P. (2014). Structural study of triazole and amide containing anion-templated pseudorotaxanes. Crystal Growth and Design [Online] 14:3472-3479. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84903741017&partnerID=40&md5=40028794dcee3341f31d8abe35a9a312.
    The ability of a range of halides and oxoanions to template pseudorotaxane formation between an isophthalamide containing macrocycle and either bis-triazole pyridinium or bis-amide pyridinium threading components was investigated. Solution 1H NMR experiments reveal that all of the studied anions (Cl-, Br-, I-, NO 3 -, HSO4 -, OAc-, and BzO-) can template interpenetrated assemblies. The solid-state structures of nine of the pseudorotaxanes were determined by single crystal X-ray structural analysis. In the solid state, the oxoanions nitrate, acetate and benzoate display much stronger hydrogen bonding with the macrocycle and threading components than the halide anions. Conversely, aromatic donor-acceptor contacts between the macrocycle and thread are significantly longer in the oxoanion templated pseudorotaxanes, presumably due to the greater steric demands of these larger templates. © 2014 American Chemical Society.
  • Knighton, R. et al. (2013). Fluorogenic dansyl-ligated gold nanoparticles for the detection of sulfur mustard by displacement assay. Chemical Communications [Online] 49:2293-2295. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84875933405&partnerID=40&md5=8406307db8e618e5786e403327d21641.
    The dansyl fluorophore ligated to gold nanoparticles via imidazole and amine groups affords conjugates capable of detecting micromolar concentrations of the chemical warfare agent sulfur mustard by a fluorescence switching 'ON' displacement assay. This journal is © The Royal Society of Chemistry.
  • Caballero, A. et al. (2013). Iodo-imidazolium salts: Halogen bonding in crystals and anion-templated pseudorotaxanes. CrystEngComm [Online] 15:3076-3081. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84876715791&partnerID=40&md5=18eb0ae925d7fecd5198694348ec5d49.
    The 2-iodoimidazolium group is exploited in the anion-templated assembly of pseudorotaxanes with isophthalamide containing macrocycles. Crystallographic and solution-phase studies illustrate that the iodo-imidazolium motif is a potent halogen bond donor, forming the most stable interpenetrated assemblies in solution with the chloride anion template. © 2013 The Royal Society of Chemistry.
  • Serpell, C. et al. (2013). Haloaurate and halopalladate imidazolium salts: Structures, properties, and use as precursors for catalytic metal nanoparticles. Dalton Transactions [Online] 42:1385-1393. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84872071627&partnerID=40&md5=78f065888abcaea8bacb37edf191bd0c.
    The synthesis and characterisation of a series of new gold- and palladium-containing symmetrical imidazolium salts are described which display significant cation-dependent effects determined by the structure of the alkyl chains of the imidazolium motifs. Whereas direct reduction of the Pd salts can produce stable nanoparticles (NPs) coated by imidazolium salts, the addition of strong base to the Pd or Au salts before reduction gives stable NPs, potentially pacified by N-heterocyclic carbene units. The possibility of NP surface protection by metal-carbon bonds in these systems is investigated by spectroscopic, synthetic, and catalytic investigations, providing support for the hypothesis. Significantly, the catalytic activity of the NPs is not inhibited by the continued presence of the ligands. © The Royal Society of Chemistry 2013.
  • Serpell, C. and Beer, P. (2013). Intermolecular interactions in bromo-, methyl-, and cyanoimidazole derivatives. Crystal Growth and Design [Online] 13:2866-2871. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84879867574&partnerID=40&md5=3773293dc88196436ba8d88d9e74fffb.
    Materials containing bistable N-H�N hydrogen bonds, such as imidazole crystals, show promise for applications in electronics. Herein, we examine the effect of imidazole functionalization upon structural parameters relating to proton transfer, molecular rotation, and order-disorder transitions. Three different substituents are studied: methyl-, bromo-, and cyano-, resulting in steric, electronic, and supramolecular modification of the imidazole core. © 2013 American Chemical Society.
  • Edwardson, T. et al. (2013). Site-specific positioning of dendritic alkyl chains on DNA cages enables their geometry-dependent self-assembly. Nature Chemistry [Online] 5:868-875. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84884852595&partnerID=40&md5=629ca8d7a0b11f95f3fcaad7f1a64d54.
    Nature uses a combination of non-covalent interactions to create a hierarchy of complex systems from simple building blocks. One example is the selective association of the hydrophobic side chains that are a strong determinant of protein organization. Here, we report a parallel mode of assembly in DNA nanotechnology. Dendritic alkyl-DNA conjugates are hybridized to the edges of a DNA cube. When four amphiphiles are on one face, the hydrophobic residues of two neighbouring cubes engage in an intermolecular 'handshake', resulting in a dimer. When there are eight amphiphiles (four on the top and bottom cube faces, respectively), they engage in an intramolecular 'handshake' inside the cube. This forms the first example of a monodisperse micelle within a DNA nanostructure that encapsulates small molecules and releases them by DNA recognition. Creating a three-dimensional pattern of hydrophobic patches, like side chains in proteins, can result in specific, directed association of hydrophobic domains with orthogonal interactions to DNA base-pairing. © 2013 Macmillan Publishers Limited. All rights reserved.
  • Evans, N. et al. (2012). Amide and urea ferrocene-containing macrocycles capable of the electrochemical sensing of anions. European Journal of Inorganic Chemistry [Online]:939-944. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84856944204&partnerID=40&md5=60b300dc262f7f24aa9ea0ef4fc66e8b.
    Two novel macrocycles that incorporate the redox-active ferrocene motif have been synthesized. The amide-containing macrocycle is capable of sensing basic oxoanions such as dihydrogen phosphate and benzoate despite only exhibiting weak binding of these anions. The second macrocycle, which incorporates urea functionality, is capable of binding and sensing a greater range of anions with a maximum shift of the ferrocene/ferrocenium redox couple of -170 mV observed upon addition of an excess amount of dihydrogen phosphate. Two macrocycles that incorporate the redox-active ferrocene motif for anion sensing are presented. The urea macrocycle binds anions more strongly than the amide macrocycle and exhibits greater shifts of the ferrocene/ferrocenium redox couple upon the addition of anions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • McConnell, A., Serpell, C. and Beer, P. (2012). Extending the family of heteroditopic calix[4]diquinone receptors for cooperative and ion-pair recognition. New Journal of Chemistry [Online] 36:102-112. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84255186383&partnerID=40&md5=231570e7fc274c5ea0dd85234af88c2a.
    New heteroditopic calix[4]diquinone receptors with different anion binding units and calix[4]diquinone scaffolds have been synthesised. Ion-pair binding studies using UV/visible and 1H NMR spectroscopies reveal that receptors 1, 2 and 4 are cooperative AND ion-pair receptors, which display little affinity for 'free' ions but enhanced binding of the ion-pairs NaCl, NH 4Cl and KCl. The more preorganised receptor 2 binds the ion-pairs more weakly than receptor 1. Varying the nature of the calix[4]diquinone scaffold appears to have little effect on ion-pair binding, although the calix[4]diquinone framework is more conformationally flexible than the tert-butylcalix[4]diquinone one and can be synthesised using the milder oxidant chlorine dioxide. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
  • Evans, N. et al. (2012). Solution and surface-confined chloride anion templated redox-active ferrocene catenanes. Chemical Science [Online] 3:1080-1089. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84858067843&partnerID=40&md5=cc589d43b27e0e4b77ef6bd733427a1c.
    The first examples of ferrocene containing catenanes, in solution and assembled on a surface are described. Chloride anion templation is exploited to synthesize redox-active [2]- and [3]-catenanes via Grubbs' ring closing metathesis, utilizing a novel ferrocene-appended isophthalamide macrocycle. X-ray crystal structures of both catenanes were determined. The ability of the [2]catenane to selectively bind and characteristically sense its chloride anion template is demonstrated by use of 1H NMR and electrochemical voltammetric techniques. Self-assembled monolayers of analogous surface-confined catenanes have been prepared on gold. In addition to being characterized by cyclic voltammetry and ellipsometry, detailed information regarding the structure of the catenane monolayers has been provided by use of angle integrated high resolution X-ray photoelectron spectroscopy. This journal is © 2012 The Royal Society of Chemistry.
  • Evans, N., Serpell, C. and Beer, P. (2011). A meta-xylenediamide macrocycle containing rotaxane anion host system constructed by a new synthetic clipping methodology. New Journal of Chemistry [Online] 35:2047-2053. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-80053368528&partnerID=40&md5=48bf8db87ccf8aa797a2970d72e369cb.
    A novel rotaxane containing a meta-xylenediamide macrocycle is prepared by a new clipping methodology. Upon anion metathesis to the non-coordinating hexafluorophosphate salt, the rotaxane host system was shown to bind chloride and bromide anions more strongly than the basic oxoanions dihydrogen phosphate and acetate in the competitive solvent system 1:1 CDCl 3:CD 3OD. © 2011 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
  • Serpell, C. et al. (2011). Core@shell bimetallic nanoparticle synthesis via anion coordination. Nature Chemistry [Online] 3:478-483. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-79957438698&partnerID=40&md5=eb877b2692cdc1e87e9f91ae4cb34df8.
    Core@shell structured bimetallic nanoparticles are currently of immense interest due to their unique electronic, optical and catalytic properties. However, their synthesis is non-trivial. We report a new supramolecular route for the synthesis of core@shell nanoparticles, based on an anion coordination protocol-the first to function by binding the shell metal to the surface of the pre-formed primary metal core before reduction. The resultant gold/palladium and platinum/palladium core@shell nanoparticles have been characterized by aberration-corrected scanning transmission electron microscopy (as well as other techniques), giving striking atomic-resolution images of the core@shell architecture, and the unique catalytic properties of the structured nanoparticles have been demonstrated in a remarkable improvement of the selective production of industrially valuable chloroaniline from chloronitrobenzene. © 2011 Macmillan Publishers Limited. All rights reserved.
  • Evans, N., Serpell, C. and Beer, P. (2011). Chloride anion templated synthesis and crystal structure of a handcuff catenane. Angewandte Chemie - International Edition [Online] 50:2507-2510. Available at: https://doi.org/10.1002/anie.201007741.
    Chloride, you're nicked! A novel handcuff catenane was prepared by anion templation and Ï?-Ï? stacking interactions. In addition, the first crystal structure determination of such a catenane is reported (see picture). Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Serpell, C. et al. (2011). Dimeric self-association of an isophthalamide macrocycle in solution and the solid state. CrystEngComm [Online] 13:4586-4591. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-79959789064&partnerID=40&md5=a943c750d7606fa6c60036e418b39b25.
    An isophthalamide macrocycle used in anion-templated interpenetrated structures is found to participate in dimeric self-assembly throughout eight different crystal forms. Analysis of these, in combination with solution-phase NMR studies, reveals the nature of the hydrogen-bonded self-association, yielding new perspectives and potential applications for the macrocycle system. © The Royal Society of Chemistry 2011.
  • Evans, N., Serpell, C. and Beer, P. (2011). A [2]catenane displaying pirouetting motion triggered by debenzylation and locked by chloride anion recognition. Chemistry - A European Journal [Online] 17:7734-7738. Available at: https://doi.org/10.1002/chem.201101033.
    Chloride locks the rings: Debenzylation of a chloride-templated N-benzyl pyridinium catenane, allows for a 180° "pirouetting" of the rings in the resulting neutral pyridyl catenane (see scheme). The catenane may be returned to its original co-conformation by chloride recognition as evidenced in solution and in the solid state. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Leontiev, A. et al. (2011). Cation-induced molecular motion of spring-like [2]catenanes. Chemical Science [Online] 2:922-927. Available at: https://doi.org/10.1039/c1sc00034a.
    The syntheses and cation recognition studies of two novel heteroditopic [2]catenanes that are capable of reversible rotary motion are described. Prepared by chloride anion templation, both catenanes possess a calixdiquinone unit able to bind Na+, K+, NH4 + and Ba2+ cations. Following characterization of thesalts of both catenanes by NMR, mass spectrometry and crystal structure determination, hexafluorophosphate salts were investigated for their behaviour upon addition of cations. Ba2+ complexation caused a partial intra-ring rotation of the two macrocycles in both species, which was reversed upon addition of the sequestering SO4 2- anion. © The Royal Society of Chemistry 2011.
  • Serpell, C. et al. (2011). Chloride anion triggered motion in a bis-imidazolium rotaxane. Dalton Transactions [Online] 40:12052-12055. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-79959810667&partnerID=40&md5=4ea58f0d619a911f3c2860ab8c44d2c5.
    We report the first bis-imidazolium-containing rotaxane, synthesised via anion templated self-assembly. Its co-conformation is controlled by a chloride anion recognition mechanism, thus demonstrating the viability of this protocol as a stimulus for shuttling molecular motion. © 2011 The Royal Society of Chemistry.
  • Evans, N., Serpell, C. and Beer, P. (2011). A redox-active [3]rotaxane capable of binding and electrochemically sensing chloride and sulfate anions. Chemical Communications [Online] 47:8775-8777. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-79960957827&partnerID=40&md5=77c973a1323b695adf7013eb05b01c18.
    A ferrocene functionalised redox-active [3]rotaxane which contains two interlocked anion recognition sites has been prepared by chloride anion templation. With chloride two equivalents of anion are bound, one in each of the interlocked cavities, while sulfate forms a 1:1 stoichimetric sandwich type complex; the rotaxane can also electrochemically sense the two anions in acetonitrile. © 2011 The Royal Society of Chemistry.
  • Serpell, C. et al. (2011). A dual-functional tetrakis-imidazolium macrocycle for supramolecular assembly. Chemical Science [Online] 2:494-500. Available at: https://doi.org/10.1039/c0sc00511h.
    A new versatile tetrakis-imidazolium macrocycle for use in supramolecular applications is reported. It displays excellent affinities for p-electron rich neutral guests such as 1,5-dihydroxynaphthalene derivatives and TTF, providing opportunities for the construction of interlocked molecules, as well as exhibiting extensive and potent anion coordination chemistry. © The Royal Society of Chemistry 2011.
  • Evans, N. et al. (2011). Anion templated assembly of [2]catenanes capable of chloride anion recognition in aqueous solvent media. RSC Advances [Online] 1:995-1003. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-84858026185&partnerID=40&md5=48663a9fc8ac6781c0f55968b6ff4a8a.
    An anion templated double cyclization strategy to synthesize [2]catenanes in which two identical acyclic pyridinium receptor motifs interweave around a chloride anion template is described. Ring closing metathesis (RCM) of the preorganized orthogonal precursor chloride complex facilitates the isolation of [2]catenanes in very high yields. X-ray crystal structures provide an insight of the supramolecular forces responsible for chloride anion templated efficacy and recognition. Removal of the chloride anion template generates topologically unique interlocked binding cavities for anions. 1H NMR anion binding investigations demonstrate the catenanes to be highly selective hosts for chloride in preference to more basic monocharged oxoanions. In aqueous solvent media containing 30% water, such catenanes exclusively bind chloride, under which conditions no binding of acetate or dihydrogen phosphate is observed. Molecular dynamic simulations in the solution phase are used to account for the catenanes' anion recognition properties. This journal is © The Royal Society of Chemistry 2011.
  • Spence, G. et al. (2011). Investigating the imidazolium-anion interaction through the anion-templated construction of interpenetrated and interlocked assemblies. Chemistry - A European Journal [Online] 17:12955-12966. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-80555135854&partnerID=40&md5=0be892971f4d91b77ac9b658711d9fe5.
    The interaction between imidazolium cations and coordinating anions is investigated through the anion-templated assembly of interpenetrated and interlocked structures. The orientation of the imidazolium motif with respect to anion binding, and hence the hydrogen bond donor arrangement, was varied in acyclic receptors, interpenetrated assemblies, and the first mono-imidazolium interlocked systems. Their anion recognition properties and co-conformations were studied by solution-phase 1H NMR investigations, solid-state structures, molecular dynamics simulations, and density functional theory calculations. Our findings suggest that the imidazolium-anion binding interaction is dominated by electrostatics with hydrogen-bonding contributions having weak orientational dependence. Imidazolium interpenetrated and interlocked assemblies: The interaction between imidazolium cations and coordinating anions is investigated through the anion-templated assembly of interpenetrated and interlocked structures. The orientation of the imidazolium motif with respect to anion binding was varied (see picture) and the anion recognition properties and co-conformations of these systems were studied by solution-phase, solid-state and computational investigations. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Hancock, L. et al. (2011). A new synthetic route to chloride selective [2]catenanes. Chemical Communications [Online] 47:1725-1727. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-79251515173&partnerID=40&md5=b252d3abe59942f42290d589cb04865a.
    A novel anion templation route has been developed to synthesise two new catenanes, which are observed to selectively complex chloride in protic solvent media. © 2011 The Royal Society of Chemistry.
  • Evans, N. et al. (2011). A 1,2,3,4,5-pentaphenylferrocene-stoppered rotaxane capable of electrochemical anion recognition. Chemistry - A European Journal [Online] 17:12347-12354. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-80054767604&partnerID=40&md5=df000791695ef525eae5d08edfa42568.
    The chloride anion templated synthesis of an electrochemical anion sensory interlocked host system, prepared by the integration of redox-active 1,2,3,4,5-pentaphenylferrocene stopper groups into the structure of a rotaxane capable of binding anionic guests is described. Extensive 1H NMR and electrochemical titration investigations were used to probe the anion recognition and sensing properties of the rotaxane, compared to the axle and model system components. A characteristic electrochemical response was observed for chloride binding by the rotaxane, which was attributed to the topologically constrained cavity of the interlocked host molecule. Topologically constrained host cavity for sensing chloride ions: Chloride anion templated synthesis of an electrochemical, anion sensory, interlocked host system, prepared by the integration of redox-active 1,2,3,4,5-pentaphenylferrocene stopper groups into the structure of a rotaxane (see picture), is described. A characteristic electrochemical response for chloride binding by the rotaxane is observed, attributed to the topologically constrained cavity of the interlocked molecule. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • McConnell, A. et al. (2010). Calix[4]arene-based rotaxane host systems for anion recognition. Chemistry - A European Journal [Online] 16:1256-1264. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-76549101257&partnerID=40&md5=945260492fba474b0c0970e24c47ea6c.
    The synthesis, structure and anion binding properties of the first calix[4]arene-based [2]rotaxane anion host systems are described. Rotaxanes 9·Cl and 12·Cl, consisting of a calix[4]-arene functionalised macrocycle wheel and different pyridinium axle components, are prepared via adaption of an anion templated synthetic strategy to investigate the effect of preorganisation of the interlocked host's binding cavity on anion binding. Rotaxane 12·Cl contains a conformationally flexible pyridinium axle, whereas rotaxane 9·Cl incorporates a more preorganised pyridinium axle component. The X-ray crystal structure of 9·Cl and solution phase 1H NMR spectroscopy demonstrate the successful interlocking of the calix[4]arene macrocycle and pyridinium axle components in the rotaxane structures. Following removal of the chloride anion template, anion binding studies on the resulting rotaxanes 9·PF6 and 12·PF 6 reveal the importance of preorganisation of the host binding cavity on anion binding. The more preorganised rotaxane 9·PF6 is the superior anion host system. The interlocked host cavity is selective for chloride in 1:1 CDCl3/CD3OD and remains selective for chloride and bromide in 10% aqueous media over the more basic oxoanions. Rotaxane 12·PF6 with a relatively conformationally flexible binding cavity is a less effective and discriminating anion host system although the rotaxane still binds halide anions in preference to oxoanions. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Serpell, C. et al. (2010). Halogen bond anion templated assembly of an imidazolium pseudorotaxane. Angewandte Chemie - International Edition [Online] 49:5322-5326. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-77954838933&partnerID=40&md5=f48d56b49149d7857418afca6669ba7a.
    Halogen bonding has been exploited in the assembly of an interpenetrated molecular system. The strength of chloride-anion-templated pseudorotaxane formation with a 2-bromo-functionalized imidazolium threading component and an isophthalamide macrocycle (see picture) is significantly enhanced compared to hydrogen-bonded pseudorotaxane analogues. (Figure Presented). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
  • Cookson, J. et al. (2010). Metal-directed assembly of large dinuclear copper(II) dithiocarbamate macrocyclic complexes. Inorganica Chimica Acta [Online] 363:1195-1203. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-77949491099&partnerID=40&md5=2798abeabeab9b434d98e233fba6c3e4.
    The synthesis of a range of dinuclear Cu(II) dithiocarbamate (dtc)-based macrocycles and their characterisation are described. By carefully tuning the size of the aromatic spacer, cavities of different dimensions can be designed. The length and flexibility of the chosen spacer group dictates the intermetallic distance and hence the degree of communication between the two metal centres as evidenced by electrochemical and EPR experiments. This is illustrated by crystallographic evidence that show the macrocycles can host guests (such as CH2Cl2) or can fold and form unexpected Cu(I) dtc clusters. © 2009 Elsevier B.V. All rights reserved.
  • Kilah, N. et al. (2010). Enhancement of anion recognition exhibited by a halogen-bonding rotaxane host system. Journal of the American Chemical Society [Online] 132:11893-11895. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-77956085939&partnerID=40&md5=32fabebea0a846ccf789e8cee4607a6a.
    We report the first use of solution-phase halogen bonding to control and facilitate the assembly of an interlocked structure through the bromide anion-templated formation of a rotaxane based upon an iodotriazolium axle. The incorporation of a halogen atom into the rotaxane host cavity dramatically improves the anion-recognition capabilities of the interlocked receptor, giving unusual iodide selectivity in a competitive aqueous medium. © 2010 American Chemical Society.
  • Hancock, L. et al. (2010). Rotaxanes capable of recognising chloride in aqueous media. Chemistry - A European Journal [Online] 16:13082-13094. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-78649256020&partnerID=40&md5=e71d7487c5dae3e1cc8c8a0d633dc09f.
    A new, versatile chloride-anion-templating synthetic pathway is exploited for the preparation of a series of eight new [2]rotaxane host molecules, including the first sulfonamide interlocked system. 1H NMR spectroscopic titration investigations demonstrate the rotaxanes' capability to selectively recognise the chloride anion in competitive aqueous solvent media. The interlocked host's halide binding affinity can be further enhanced and tuned through the attachment of electron-withdrawing substituents and by increasing its positive charge. A dicationic rotaxane selectively binds chloride in 35 % water, wherein no evidence of oxoanion binding is observed. NMR spectroscopy, X-ray structural analysis and computational molecular dynamics simulations are used to account for rotaxane formation yields, anion binding strengths and selectivity trends. Chloride wins: A new, versatile chloride-anion-templating synthetic pathway is exploited in the preparation of a series of eight new [2]rotaxane host molecules (see image), including the first sulfonamide interlocked system. 1H NMR spectroscopic titration investigations demonstrate the rotaxanes' capability to recognise chloride anions in competitive aqueous solvent media, including a dicationic rotaxane that binds chloride in 35 % water. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Mullen, K. et al. (2009). Exploiting the 1,2,3-triazolium motif in anion-templated formation of a bromide-selective rotaxane host assembly. Angewandte Chemie - International Edition [Online] 48:4781-4784. Available at: http://www.scopus.com/inward/record.url?eid=2-s2.0-70349778997&partnerID=40&md5=b0d2771c7acd6d700330d7d3f2136fe6.
    Bromide is best: The first [2]rotaxane incorporating the triazolium anion-binding motif is prepared using bromide anion templation. Preliminary anion-binding investigations reveal that the rotaxane exhibits the rare selectivity preference for bromide over chloride ions. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.
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