Publications
177 results found
Wan L, Wade J, Shi X, et al., 2020, Highly Efficient Inverted Circularly Polarized Organic Light-Emitting Diodes, ACS Applied Materials & Interfaces, Vol: 12, Pages: 39471-39478, ISSN: 1944-8244
Circularly polarized (CP) electroluminescence has been demonstrated as a strategy to improve the performance of organic light-emitting diode (OLED) displays. CP emission can be generated from both small-molecule and polymer OLEDs (SM-OLEDs and PLEDs), but to date, these devices suffer from low dissymmetry factors (g-factor < 0.1), poor device performance, or a combination of the two. Here, we demonstrate the first CP-PLED employing an inverted device architecture. Through this approach, we demonstrate a highly efficient CP-PLED, with a current efficiency of 16.4 cd/A, a power efficiency of 16.6 lm/W, a maximum luminance of over 28,500 cd/m2, and a high EL dissymmetry (gEL) of 0.57. We find that the handedness of the emitted light is sensitive to the PLED device architecture: the sign of CP-EL from an identically prepared active layer reverses between inverted and conventional devices. The inverted structure affords the first demonstration of CP-PLEDs exhibiting both high efficiency and high dissymmetry—the two figures of merit which, until now, have been difficult to achieve at the same time. We also highlight device architecture and associated internal electric field to be a previously unexplored means to control the handedness of CP emission. Our findings significantly broaden the versatility of CP emissive devices and should enable their further application in a variety of other CP-dependent technologies.
Uriz-Huarte A, Date A, Ang H, et al., 2020, The transcriptional repressor REV-ERB as a novel target for disease, Bioorganic & Medicinal Chemistry Letters, Vol: 30, Pages: 127395-127395, ISSN: 0960-894X
REV-ERB is a member of the nuclear receptor superfamily of transcription factors involved in the regulation of many physiological processes, from circadian rhythm, to immune function and metabolism. Accordingly, REV-ERB has been considered as a promising, but difficult drug target for the treatment of numerous diseases. Here, we concisely review current understanding of the function of REV-ERB, modulation by endogenous factors and synthetic ligands, and the involvement of REV-ERB in select human diseases. Particular focus is placed on the medicinal chemistry of synthetic REV-ERB ligands, which demonstrates the need for higher quality ligands to aid in robust validation of this exciting target.
Rushworth J, Montgomery K, Cao B, et al., 2020, Glycosylated nanoparticles derived from RAFT polymerization for effective drug delivery to macrophages, ACS Applied Bio Materials, Vol: 3, Pages: 5775-5786, ISSN: 2576-6422
The functional group tolerance and simplicity of reversible addition fragmentation chain transfer (RAFT) polymerization enable its use in the preparation of a wide range of functional polymer architectures for a variety of applications, including drug delivery. Given the role of tumor-associated macrophages (TAMs) in cancer and their dependence on the tyrosine kinase receptor FMS (CSF-1R), the key aim of this work was to achieve effective delivery of an FMS inhibitor to cells using a polymer delivery system. Such a system has the potential to exploit biological features specific to macrophages and therefore provide enhanced selectivity. Building on our prior work, we have prepared RAFT polymers based on a poly(butyl methacrylate-co-methacrylic acid) diblock, which were extended with a hydrophilic block, a cross-linker, and a mannose-based monomer scaffold, exploiting the abundance of macrophage mannose receptors (MMRs, CD206) on the surface of macrophages. We demonstrate that the prepared polymers can be assembled into nanoparticles and are successfully internalized into macrophages, in part, via the MMR (CD206). Finally, we showcase the developed nanoparticles in the delivery of an FMS inhibitor to cells, resulting in inhibition of the FMS receptor. As such, this study lays the groundwork for further drug-delivery studies aimed at specifically targeting TAMs with molecularly targeted therapeutics.
Shi W, Salerno F, Santana-Bonilla A, et al., 2020, Fullerene Dissymmetrization as a Means to Achieve Single Enantiomer Electron Acceptors with Maximized Chiroptical Responsiveness
<jats:p>Solubilized fullerene derivatives have revolutionised the development of organic photovoltaic devices, acting as excellent electron acceptors. The addition of solubilizing addends to the fullerene cage results in a large number of isomers, which are generally employed as isomeric mixtures. Moreover, a significant number of these isomers are chiral, which further adds to the isomeric complexity. The opportunities presented by single isomer, and particularly single enantiomer, fullerenes in organic electronic materials and devices are poorly understood. Here we separate 10 pairs of enantiomers from the 19 structural isomers of bis[60]PCBM, using them to elucidate important chiroptical structure-property relationships and demonstrating their application to a single enantiomer circularly polarized (CP) light detecting device. We find that larger chiroptical responses occur through inherent chirality of the fullerene cage and particularly through transitions with low CT character. When used in a single enantiomer organic field-effect transistor device, we demonstrate the potential to discriminate CP light with a fast light response time and with a very high photocurrent dissymmetry factor (<jats:italic>g<jats:sub>ph</jats:sub></jats:italic> = ±1.35). Our study thus provides key strategies to design fullerenes with large chiroptical responses for use as single enantiomer components of organic electronic devices. We anticipate that our data will position chiral fullerenes as an exciting material class for the growing field of chiral electronic technologies.</jats:p>
Shi W, Salerno F, Santana-Bonilla A, et al., 2020, Fullerene Dissymmetrization as a Means to Achieve Single Enantiomer Electron Acceptors with Maximized Chiroptical Responsiveness
<jats:p><p>Solubilized fullerene derivatives have revolutionised the development of organic photovoltaic devices, acting as excellent electron acceptors. The addition of solubilizing addends to the fullerene cage results in a large number of isomers, which are generally employed as isomeric mixtures. Moreover, a significant number of these isomers are chiral, which further adds to the isomeric complexity. The opportunities presented by single isomer, and particularly single enantiomer, fullerenes in organic electronic materials and devices are poorly understood. Here we separate 10 pairs of enantiomers from the 19 structural isomers of bis[60]PCBM, using them to elucidate important chiroptical structure-property relationships and demonstrating their application to a single enantiomer circularly polarized (CP) light detecting device. We find that larger chiroptical responses occur through inherent chirality of the fullerene cage and particularly through transitions with low CT character. When used in a single enantiomer organic field-effect transistor device, we demonstrate the potential to discriminate CP light with a fast light response time and with a very high photocurrent dissymmetry factor (<i>g<sub>ph</sub></i> = ±1.35). Our study thus provides key strategies to design fullerenes with large chiroptical responses for use as single enantiomer components of organic electronic devices. We anticipate that our data will position chiral fullerenes as an exciting material class for the growing field of chiral electronic technologies.</p></jats:p>
Schmidt JA, Weatherby JA, Sugden I, et al., 2020, Computational Screening of Organic Semiconductors: Exploring Side-Group Functionalisation and Assembly to Optimise Charge Transport in Chiral Molecules
<jats:p>Molecular materials are challenging to design as their packing arrangement and hence properties are subject to subtle variations in the interplay of soft intermolecular interactions that are difficult to predict. The rational design of new molecular materials with tailored properties is currently hampered by the lack of knowledge of how a candidate molecule will pack in space and how we can control the polymorphs we can experimentally obtain. Here, we develop a simplified approach to aid the material design process, by the development of a screening process that is used to test 1344 helicene molecules that have potential as organic electronic materials. Our approach bridges the gap between single molecule design, molecular assembly, and the resulting charge-carrier mobilities. We find that fluorination significantly improves electron transport in the molecular material by up to 200%; the reference [6]helicene packing showed a mobility of 0.30 cm2 V-1 s-1, fluorination increased the mobility to up to 0.96 and 0.97 (13-fluoro[6]H and 4,13-difluoro[6]H), assuming an outer reorganisation energy of 0.30 eV. Side groups containing triple bonds largely lead to improved transfer integrals. We validate our screening approach through the use of crystal structure prediction to confirm the presence of favourable packing motifs to maximize charge mobility.</jats:p>
Gerkman MA, Gibson RSL, Calbo J, et al., 2020, Arylazopyrazoles for long-term thermal energy storage and optically-triggered heat release below 0 °C, Journal of the American Chemical Society, Vol: 142, Pages: 8688-8695, ISSN: 0002-7863
Arylazopyrazole derivatives based on four core structures (4pzMe, 3pzH, 4pzH, and 4pzH-F2) and functionalized with a dodecanoate group were demonstrated to store thermal energy in their metastable Z isomer liquid phase and release the energy by optically triggered crystallization at −30 ℃ for the first time. Three heat storage-release schemes were discovered involving different activation methods (optical, thermal, or combined) for generating liquid-state Z isomers capable of storing thermal energy. Visible light irradiation induced the selective crystallization of the liquid phase via Z-to-E isomerization, and the latent heat stored in the liquid Z isomers was preserved for longer than two weeks unless optically triggered. Up to 92 kJ/mol of thermal energy was stored in the compounds demonstrating remarkable thermal stability of Z isomers at high temperatures and liquid-phase stability at temperatures below 0 ℃.
Wade J, Hilfiker J, Brandt JR, et al., 2020, A Unified Model to Explain the Large Chiroptical Effects in Polymer Systems Through Natural Optical Activity
<jats:p>Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by coupling of electric and magnetic transition dipole moments (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area.</jats:p>
Rueda-Zubiaurre A, Yahiya S, Fischer O, et al., 2020, Structure-activity relationship studies of a novel class of transmission blocking antimalarials targeting male gametes., Journal of Medicinal Chemistry, Vol: 63, Pages: 2240-2262, ISSN: 0022-2623
Malaria is still a leading cause of mortality among children in the developing world, and despite the immense progress made in reducing the global burden, further efforts are needed if eradication is to be achieved. In this context, targeting transmission is widely recognized as a necessary intervention towards that goal. After carrying out a screen to discover new transmission-blocking agents, herein we report our medicinal chemistry efforts to study the potential of the most robust hit, DDD01035881, as a male-gamete targeted compound. We reveal key structural features for the activity of this series and identify analogues with greater potency and improved metabolic stability. We believe this study lays the groundwork for further development of this series as a transmission blocking agent.
Kurz W, Yetisen AK, Kaito MV, et al., 2020, UV-sensitive wearable devices for colorimetric monitoring of UV exposure, Advanced Optical Materials, Vol: 8, ISSN: 2195-1071
The extensive exposure of the human epidermis to solar radiation creates a health risk that results in skin cancer. Commercial sunscreens offer sufficient protection from ultraviolet (UV) radiation; however, the ability to determine UV exposure limits can provide informed decisions about the dose of sunscreen required and the frequency of re-application. Here, a wide range of wearable devices that colorimetrically report on UV exposure are developed. Under UV radiation, UV-sensitive dyes change their color from 280 to 400 nm in the visible spectrum. By correlating the current color value and the UV dose, the amount of sun exposure is determined with an accuracy of 95%. A smartphone camera algorithm is coded to automatically perform the color analysis of these dyes. The UV-sensitive dyes are incorporated in wearable devices, skin patches, textiles, contact lenses, and tattoo inks. The developed wearable devices will ensure monitoring UV radiation to rationally manage the user's behavior in order to prevent harmful sun exposure.
Calbo J, Thawani AR, Gibson RSL, et al., 2019, A combinatorial approach to improving the performance of azoarene photoswitches, BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY, Vol: 15, Pages: 2753-2764, ISSN: 1860-5397
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- Citations: 37
Wan L, Wade J, Salerno F, et al., 2019, Inverting the handedness of circularly polarized luminescence from light-emitting polymers using film thickness, ACS Nano, Vol: 13, Pages: 8099-8105, ISSN: 1936-0851
The emission of circularly polarized light is central to many applications, including data storage, optical quantum computation, biosensing, environmental monitoring, and display technologies. An emerging method to induce (chiral) circularly polarized (CP) electroluminescence from the active layer of polymer light-emitting diodes (polymer OLEDs; PLEDs) involves blending achiral polymers with chiral small-molecule additives, where the handedness/sign of the CP light is controlled by the absolute stereochemistry of the small molecule. Through the in-depth study of such a system we report an interesting chiroptical property: the ability to tune the sign of CP light as a function of active layer thickness for a fixed enantiomer of the chiral additive. We demonstrate that it is possible to achieve both efficient (4.0 cd/A) and bright (8000 cd/m2) CP-PLEDs, with high dissymmetry of emission of both left-handed (LH) and right-handed (RH) light, depending on thickness (thin films, 110 nm: gEL = 0.51, thick films, 160 nm: gEL = -1.05, with the terms "thick" and "thin" representing the upper and lower limits of the thickness regime studied), for the same additive enantiomer. We propose that this arises due to an interplay between localized CP emission originating from molecular chirality and CP light amplification or inversion through a chiral medium. We link morphological, spectroscopic, and electronic characterization in thin films and devices with theoretical studies in an effort to determine the factors that underpin these observations. Through the control of active layer thickness and device architecture, this study provides insights into the mechanisms that result in CP luminescence and high performance from CP-PLEDs, as well as demonstrating new opportunities in CP photonic device design.
Gibson R, Calbo J, Fuchter MJ, 2019, Chemical Z‐E isomer switching of arylazopyrazoles using acid, ChemPhotoChem, Vol: 3, Pages: 372-377, ISSN: 2367-0932
Arylazopyrazoles show significant potential as next‐generation photoswitches, in particular because of the high thermal stability of their Z‐isomers. Herein we investigate the potential to perform Z−E isomer chemical switching of arylazopyrazoles using acid. We show that acid‐accelerated isomerisation allows for robust Z−E switching using mild acids and opens up the possibility to use light‐acid cycles to near quantitatively and reversibly switch the arylazopyrazoles at room temperature. We attribute the chemical switching to azonium formation, facilitated by mesomeric stabilisation by the pyrazole ring. Coupled with their exceptionally long Z‐isomer half‐lives, we believe our study may open up a wider array of functional opportunities for the arylazopyrazoles.
Yahiya S, Rueda-Zubiaurre A, Delves MJ, et al., 2019, The antimalarial screening landscape-looking beyond the asexual blood stage, CURRENT OPINION IN CHEMICAL BIOLOGY, Vol: 50, Pages: 1-9, ISSN: 1367-5931
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- Citations: 17
Bardell-Cox O, White AJP, Aragón L, et al., 2019, Synthetic studies on the reverse antibiotic natural products, the nybomycins, MedChemComm, Vol: 10, Pages: 1438-1444, ISSN: 2040-2503
Antimicrobial resistance (AMR) is a serious issue that could have severe consequences if steps are not taken. The nybomycin natural products have the potential to extend the clinical efficacy of the marketed fluoroquinolone class of antibiotics through a ‘reverse antibiotic’ approach. However, only very limited structure–activity relationships are known for these fascinating compounds, in part due to challenges with their synthesis. Here we report a new scalable and robust synthetic route to the nybomycin natural products to aid in the development of this series. Through this synthesis, we report the antibiotic activity of novel analogues of this family confirming the selectivity for fluoroquinolone resistant bacteria and potential future opportunities for further optimisation.
Mercea DM, Howlett MG, Piascik AD, et al., 2019, Enantioselective reduction of N-alkyl ketimines with frustrated Lewis pair catalysis using chiral borenium ions, Chemical Communications, Vol: 55, Pages: 7077-7080, ISSN: 1359-7345
Enantioselective reduction of ketimines was demonstrated using chiral N-heterocyclic carbene (NHC)-stabilised borenium ions in frustrated Lewis pair catalysis. High levels of enantioselectivity were achieved for substrates featuring secondary N-alkyl substituents. Comparative reactivity and mechanistic studies identify key determinants required to achieve useful enantioselectivity and represent a step forward in the further development of enantioselective FLP methodologies.
Salerno F, Rice B, Schmidt JA, et al., 2019, The influence of nitrogen position on charge carrier mobility in enantiopure aza[6]helicene crystals, Physical Chemistry Chemical Physics, Vol: 21, Pages: 5059-5067, ISSN: 1463-9076
The properties of an organic semiconductor are dependent on both the chemical structure of the molecule involved, and how it is arranged in the solid-state. It is challenging to extract the influence of each individual factor, as small changes in the molecular structure often dramatically change the crystal packing and hence solid-state structure. Here, we use calculations to explore the influence of the nitrogen position on the charge mobility of a chiral organic molecule when the crystal packing is kept constant. The transfer integrals for a series of enantiopure aza[6]helicene crystals sharing the same packing were analysed in order to identify the best supramolecular motifs to promote charge carrier mobility. The regioisomers considered differ only in the positioning of the nitrogen atom in the aromatic scaffold. The simulations showed that even this small change in the chemical structure has a strong effect on the charge transport in the crystal, leading to differences in charge mobility of up to one order of magnitude. Some aza[6]helicene isomers that were packed interlocked with each other showed high HOMO-HOMO integrals (up to 70 meV), whilst molecules arranged with translational symmetry generally afforded the highest LUMO-LUMO integrals (40-70 meV). As many of the results are not intuitively obvious, a computational approach provides additional insight into the design of new semiconducting organic materials.
Chavas TEJ, Fuchter MJ, DiMaggio PA, 2018, Unbiased mass spectrometry elucidation of the targets and mechanisms of activity-based probes: A case study involving sulfonyl fluorides, ACS Chemical Biology, Vol: 13, Pages: 2897-2907, ISSN: 1554-8929
The elucidation of protein/drug interactions remains a major challenge in drug discovery. Liquid chromatography–tandem mass spectrometry has emerged as a tremendously powerful technology for this endeavor, but its full potential has yet to be realized owing in part to unresolved challenges in data analysis. Herein, we demonstrate how tandem mass spectrometry can comprehensively map small molecule/peptide adducts when combined with unconstrained sequencing. Using a published sulfonyl fluoride activity-based probe as a model system, this method enabled the discovery of several unreported sites of interaction with its target proteins. Crucially, this probe was found to undergo quantitative displacement and hydrolysis from the target protein’s active site. Isotopic labeling experiments provided a mechanistic rationale for the observed hydrolysis that involves neighboring-group participation. A chemical biology tagging strategy that leverages the probe’s observed lability was developed and shown to be compatible with the original small molecule inhibitor in discovery profiling experiments.
Delves M, Miguel-Blanco C, Matthews H, et al., 2018, A high throughput screen for next-generation leads targeting malaria parasite transmission, Nature Communications, Vol: 9, ISSN: 2041-1723
Spread of parasite resistance to artemisinin threatens current frontline antimalarial therapies, highlighting the need for new drugs with alternative modes of action. Since only 0.2–1% of asexual parasites differentiate into sexual, transmission-competent forms, targeting this natural bottleneck provides a tangible route to interrupt disease transmission and mitigate resistance selection. Here we present a high-throughput screen of gametogenesis against a ~70,000 compound diversity library, identifying seventeen drug-like molecules that target transmission. Hit molecules possess varied activity profiles including male-specific, dual acting male–female and dual-asexual-sexual, with one promising N-((4-hydroxychroman-4-yl)methyl)-sulphonamide scaffold found to have sub-micromolar activity in vitro and in vivo efficacy. Development of leads with modes of action focussed on the sexual stages of malaria parasite development provide a previously unexplored base from which future therapeutics can be developed, capable of preventing parasite transmission through the population.
Fuchter MJ, 2018, Editorial, BIOORGANIC & MEDICINAL CHEMISTRY, Vol: 26, Pages: 2919-2920, ISSN: 0968-0896
Rice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018, A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral [6]helicene molecule (vol 10, pg 1865, 2018), NANOSCALE, Vol: 10, Pages: 9410-9410, ISSN: 2040-3364
Ashley AE, Fuchter MJ, Tighe C, et al., 2018, Direct reductive amination of carbonyl compounds catalyzed by a moisture tolerant Tin (IV) Lewis acid, Advanced Synthesis and Catalysis, Vol: 360, Pages: 1066-1071, ISSN: 1615-4150
Despite the ever-broadening applications of main-group ‘frustrated Lewis pair’ (FLP) chemistry to both new and established reactions, their typical intolerance of water, especially at elevated temperatures (>100 °C), represents a key barrier to their mainstream adoption. Herein we report that FLPs based on the Lewis acid iPr3SnOTf are moisture tolerant in the presence of moderately strong nitrogenous bases, even under high temperature regimes, allowing them to operate as simple and effective catalysts for the reductive amination of organic carbonyls, including for challenging bulky amine and carbonyl substrate partners.
Ali S, Patel H, Periyasamy M, et al., 2018, ICEC0942, an orally bioavailable selective inhibitor of CDK7 for cancer treatment, Molecular Cancer Therapeutics, ISSN: 1535-7163
Recent reports indicate that some cancer types are especially sensitive to transcription inhibition, suggesting that targeting the transcriptional machinery provides new approaches to cancer treatment. Cyclin-dependent kinase (CDK)7 is necessary for transcription, and acts by phosphorylating the C-terminal domain (CTD) of RNA polymerase II (PolII) to enable transcription initiation. CDK7 additionally regulates the activities of a number of transcription factors, including Estrogen receptor-α (ER). Here we describe a new, orally bioavailable CDK7 inhibitor, ICEC0942. It selectively inhibits CDK7, with an IC50 of 40nM; IC50 values for CDK1, CDK2, CDK5 and CDK9 were 45-, 15-, 230- and 30-fold higher. In vitro studies show that a wide range of cancer types are sensitive to CDK7 inhibition with GI50 values ranging between 0.2-0.3 µM. In xenografts of both breast and colorectal cancers, the drug has substantial anti-tumor effects. Additionally, combination therapy with tamoxifen showed complete growth arrest of ER-positive tumor xenografts. Our findings reveal that CDK7 inhibition provides a new approach, especially for ER-positive breast cancer and identify ICEC0942 as a prototype drug with potential utility as a single agent or in combination with hormone therapies for breast cancer. ICEC0942 may also be effective in other cancers that display characteristics of transcription factor addiction, such as acute leukaemia, and small-cell lung cancer.
Lubin AS, Zubiaurre AR, Matthews H, et al., 2018, Development of a photo-crosslinkable diaminoquinazoline inhibitor for target identification in plasmodium falciparum, ACS Infectious Diseases, Vol: 4, Pages: 523-530, ISSN: 2373-8227
Diaminoquinazolines represent a privileged scaffold for antimalarial discovery, including use as putative Plasmodium histone lysine methyltransferase inhibitors. Despite this, robust evidence for their molecular targets is lacking. Here we report the design and development of a small-molecule photo-crosslinkable probe to investigate the targets of our diaminoquinazoline series. We demonstrate the effectiveness of our designed probe for photoaffinity labelling of Plasmodium lysates and identify similarities between the target profiles of the probe and the representative diaminoquinazoline BIX-01294. Initial pull-down proteomics experiments identified 104 proteins from different classes, many of which are essential, highlighting the suitability of the developed probe as a valuable tool for target identification in Plasmodium falciparum.
Hazel P, Kroll SHB, Bondke A, et al., 2018, Corrigendum: Inhibitor selectivity for cyclin-dependent kinase 7: a structural, thermodynamic, and modelling study, ChemMedChem, Vol: 13, Pages: 207-207, ISSN: 1860-7187
Rice B, LeBlanc LM, Otero-de-la-Roza A, et al., 2018, A computational exploration of the crystal energy and charge-carrier mobility landscapes of the chiral [6]helicene molecule, Nanoscale, Vol: 10, Pages: 1865-1876, ISSN: 2040-3364
The potential of a given π-conjugated organic molecule in an organic semiconductor device is highly dependent on molecular packing, as it strongly influences the charge-carrier mobility of the material. Such solid-state packing is sensitive to subtle differences in their intermolecular interactions and is challenging to predict. Chirality of the organic molecule adds an additional element of complexity to intuitive packing prediction. Here we use crystal structure prediction to explore the lattice-energy landscape of a potential chiral organic semiconductor, [6]helicene. We reproduce the experimentally observed enantiopure crystal structure and explain the absence of an experimentally observed racemate structure. By exploring how the hole and electron-mobility varies across the energy–structure–function landscape for [6]helicene, we find that an energetically favourable and frequently occurring packing motif is particularly promising for electron-mobility, with a highest calculated mobility of 2.9 cm2 V−1 s−1 (assuming a reorganization energy of 0.46 eV). We also calculate relatively high hole-mobility in some structures, with a highest calculated mobility of 2.0 cm2 V−1 s−1 found for chains of helicenes packed in a herringbone fashion. Neither the energetically favourable nor high charge-carrier mobility packing motifs are intuitively obvious, and this demonstrates the utility of our approach to computationally explore the energy–structure–function landscape for organic semiconductors. Our work demonstrates a route for the use of computational simulations to aid in the design of new molecules for organic electronics, through the a priori prediction of their likely solid-state form and properties.
Montgomery KS, Davidson RWM, Cao B, et al., 2017, Effective macrophage delivery using RAFT copolymer derived nanoparticles, Polymer Chemistry, Vol: 9, Pages: 131-137, ISSN: 1759-9954
Reversible addition fragmentation chain transfer (RAFT) polymerisation provides a highly controlled means to assemble copolymers of different architectures for a variety of applications, including drug delivery. Polymers consisting of a butyl methacrylate-co-methacrylic acid p(BMA-co-MAA) hydrophobic block and a poly(ethylene glycol) methyl ether methacrylate p(PEGMA-475) hydrophilic block were synthesised via RAFT polymerisation and self-assembled into micelles. A range of micelle particles of different sizes were obtained by varying the composition of the block copolymers. The micelles were crosslinked to form nanoparticles and fluorescently labelled to study cellular internalisation. The prepared nanoparticles were extensively taken up by primary murine macrophages and a promising candidate was identified. To demonstrate effective delivery of a cell impenetrable cargo a fluorescent dye, 4′,6-diamidino-2-phenylindole (DAPI), was encapsulated inside the nanoparticles and successfully delivered to macrophages. The nanoparticles’ stability at increased temperatures and at low concentrations, the tunability of their synthesis and their extensive internalisation by macrophages and performance makes them highly promising delivery vehicles for a range of therapeutics and imaging agents.
Yang Y, Rice B, Shi X, et al., 2017, Emergent Properties of an Organic Semiconductor Driven by its Molecular Chirality, ACS Nano, Vol: 11, Pages: 8329-8338, ISSN: 1936-0851
Chiral molecules exist as pairs of nonsuperimposable mirror images; a fundamental symmetry property vastly underexplored in organic electronic devices. Here, we show that organic field-effect transistors (OFETs) made from the helically chiral molecule 1-aza[6]helicene can display up to an 80-fold difference in hole mobility, together with differences in thin-film photophysics and morphology, solely depending on whether a single handedness or a 1:1 mixture of left- and right-handed molecules is employed under analogous fabrication conditions. As the molecular properties of either mirror image isomer are identical, these changes must be a result of the different bulk packing induced by chiral composition. Such underlying structures are investigated using crystal structure prediction, a computational methodology rarely applied to molecular materials, and linked to the difference in charge transport. These results illustrate that chirality may be used as a key tuning parameter in future device applications.
Brandt JR, Pospíšil L, Bednárová L, et al., 2017, Intense Redox-Driven Chiroptical Switching with a 580 mV Hysteresis Actuated Through Reversible Dimerization of an Azoniahelicene, Chemical Communications, Vol: 53, Pages: 9059-9062, ISSN: 1364-548X
Electrochemical reduction of an azoniahelicene affords a dimer, accompanied by a strong change in the electronic circular dichroism. The fast dimerisation event leads to a >500 mV shift of the oxidation potential, affording a large area of bistability, where the chiroptical signal only depends on the redox history.
Scott DJ, Fuchter MJ, Ashley AE, 2017, Designing effective ‘frustrated Lewis pair’ hydrogenation catalysts, Chemical Society Reviews, Vol: 46, Pages: 5689-5700, ISSN: 1460-4744
The past decade has seen the subject of transition metal-free catalytic hydrogenation develop incredibly rapidly, transforming from a largely hypothetical possibility to a well-established field that can be applied to the reduction of a diverse variety of functional groups under mild conditions. This remarkable change is principally attributable to the development of so-called ‘frustrated Lewis pairs’: unquenched combinations of bulky Lewis acids and bases whose dual reactivity can be exploited for the facile activation of otherwise inert chemical bonds. While a number of comprehensive reviews into frustrated Lewis pair chemistry have been published in recent years, this tutorial review aims to provide a focused guide to the development of efficient FLP hydrogenation catalysts, through identification and consideration of the key factors that govern their effectiveness. Following discussion of these factors, their importance will be illustrated using a case study from our own research, namely the development of FLP protocols for successful hydrogenation of aldehydes and ketones, and for related moisture-tolerant hydrogenation.
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