12 results found
Greenfield JL, Wade J, Brandt JR, et al., 2021, Pathways to increase the dissymmetry in the interaction of chiral light and chiral molecules, CHEMICAL SCIENCE, ISSN: 2041-6520
Wade J, Brandt JR, Reger D, et al., 2021, 500‐Fold Amplification of Small Molecule Circularly Polarised Luminescence through Circularly Polarised FRET, Angewandte Chemie, Vol: 133, Pages: 224-229, ISSN: 0044-8249
Wade J, Hilfiker J, Brandt J, et al., 2020, Natural optical activity as the origin of the large chiroptical properties in π-conjugated polymer thin films, Nature Communications, Vol: 11, Pages: 1-11, ISSN: 2041-1723
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-azahelicene) 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 magneto-electric coupling (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.
Wade J, Brandt J, Reger D, et al., 2020, 500‐fold amplification of small molecule circularly polarized luminescence through circularly polarized FRET, Angewandte Chemie International Edition, ISSN: 1433-7851
Strongly dissymmetric circularly polarised (CP) luminescence from small organic molecules could transform a range of technologies, such as display devices. However, highly dissymmetric emission is usually not possible with small organic molecules, which typically give dissymmetric factors of photoluminescence ( g PL ) less than 10 ‐2 . Here we describe an almost 10 3 ‐fold chiroptical amplification of a π‐extended superhelicene when embedded in an achiral conjugated polymer matrix. This combination increases the |gPL| of the superhelicene from approximately 3 × 10 ‐4 in solution to 0.15 in a blend film in the solid‐state. We propose that the amplification arises not simply through a chiral environment effect, but instead due to electrodynamic coupling between the electric and magnetic transition dipoles of the polymer donor and superhelicene acceptor, and subsequent CP Förster resonance energy transfer. We show that this amplification effect holds across several achiral polymer hosts and thus represents a simple and versatile approach to enhance the g‐factors of small organic molecules.
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.
Yang Y, Rice B, Shi X, et al., 2018, Emergent Properties of an Organic Semiconductor Driven by its Molecular Chirality (vol 11, pg 8329, 2017), ACS NANO, Vol: 12, Pages: 6343-6343, 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-azahelicene 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.
Brandt JR, Salerno F, Fuchter MJ, 2017, The added value of small-molecule chirality in technological applications, Nature Reviews Chemistry, Vol: 1, ISSN: 2397-3358
Chirality is a fundamental symmetry property; chiral objects, such as chiral small molecules, exist as a pair of non-superimposable mirror images. Although small-molecule chirality is routinely considered in biologically focused application areas (such as drug discovery and chemical biology), other areas of scientific development have not considered small-molecule chirality to be central to their approach. In this Review, we highlight recent research in which chirality has enabled advancement in technological applications. We showcase examples in which the presence of small-molecule chirality is exploited in ways beyond the simple interaction of two different chiral molecules; this can enable the detection and emission of chiral light, help to control molecular motion, or provide a means to control electron spin and bulk charge transport. Thus, we demonstrate that small-molecule chirality is a highly promising avenue for a wide range of technologically oriented scientific endeavours.
Brandt JR, Wang X, Yang Y, et al., 2016, Circularly polarized phosphorescent electroluminescence with a high dissymmetry factor from PHOLEDs based on a platinahelicene, Journal of the American Chemical Society, Vol: 138, Pages: 9743-9746, ISSN: 1520-5126
Circularly polarized (CP) light is of interest inareas such as quantum optical computing, optical spintronics,biomedicine and high efficiency displays. Direct emissionof CP light from organic light-emitting diodes (OLEDs) hasbeen a focus of research as it has the immediate applicationof increasing efficiency and simplifying device architecture inOLED based displays. High dissymmetry (gEL) factor valueshave been reported for devices employing fluorescent polymers,but these CP-OLEDs are limited in their ultimate efficienciesby the type of emissive electronic transitions involved.In contrast, phosphorescent OLEDs (PHOLEDs) canemit light from triplet excited states and can thereforeachieve very high efficiencies. However, CP-PHOLEDs aresignificantly understudied and the two previous reports sufferedfrom very low brightness or gEL values. Here, we use aplatinahelicene complex to construct a CP-PHOLED thatachieves both a display level brightness and a high gEL factor.The dissymmetry of CP emission reached with this proof-ofconceptsingle-layer helicene-based device is sufficient toprovide real-world benefits over non-polarized emission, andpaves the way towards chiral metal complex–based CPPHOLEDdisplays.
Brandt JR, Lee E, Boursalian GB, et al., 2014, Mechanism of electrophilic fluorination with Pd(IV): fluoride capture and subsequent oxidative fluoride transfer, CHEMICAL SCIENCE, Vol: 5, Pages: 169-179, ISSN: 2041-6520
Ciana C-L, Phipps RJ, Brandt JR, et al., 2011, A Highly Para-Selective Copper(II)-Catalyzed Direct Arylation of Aniline and Phenol Derivatives, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 50, Pages: 458-462, ISSN: 1433-7851
Hart WS, Amrania H, Beckley A, et al., Label-Free Chemical Nano-Imaging of Intracellular Drug Binding Sites
Optical microscopy has a diffraction limited resolution of about 250 nm.Fluorescence methods (e.g. PALM, STORM, STED) beat this, but they are stilllimited to 10 s of nm, and the images are an indirect pointillistrepresentation of only part of the original object. Here we describe a way ofcombining a sample preparation technique taken from histopathology, with aprobe-based nano-imaging technique, (s SNOM) from the world of Solid StatePhysics. This allows us to image subcellular structures optically, and at ananoscale resolution that is about 100 x better than normal microscopes. Byadding a tuneable laser source, we also demonstrate mid-infrared chemicalnano-imaging (MICHNI) in human myeloma cells and we use it to map the bindingsites of the anti cancer drug bortezomib to less than 10 zL sized intracellularcomponents. MICHNI is label free and can be used with any biological materialand drugs with specific functional chemistry. We believe that its combinationof speed, cheapness, simplicity, safety and chemical contrast promises atransformative impact across the life sciences.
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