Publications
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Wong WWH, Subbiah J, Puniredd SR, et al., 2012, Liquid crystalline hexa-peri-hexabenzocoronene-diketopyrrolopyrrole organic dyes for photovoltaic applications, Journal of Materials Chemistry, Vol: 22, Pages: 21131-21137, ISSN: 0959-9428
A series of liquid crystalline organic dyes consisting of fluorenyl hexa-peri-hexabenzocoronene (FHBC) and diketopyrrolopyrrole (DPP) units was synthesised and characterised. Their thermotropic behaviour is a result of the strong π-π association between FHBC units while the DPP unit enhances light absorption. With small changes in the molecular structure, significant differences in molecular organisation were observed in solid state. In turn, the molecular arrangement led to variations in the semiconducting properties of these materials and, ultimately, their performance in organic solar cells. © 2012 The Royal Society of Chemistry.
Singh TB, Chen X, Wong WWH, et al., 2012, Correlation of charge extraction properties and short circuit current in various organic binary and ternary blend photovoltaic devices, Applied Physics A: Materials Science and Processing, Vol: 108, Pages: 515-520, ISSN: 0947-8396
Charge extraction properties of various binary and ternary blends of organic photovoltaic devices covering both polymers and small molecules are studied. Due to their bipolar nature, both slow and fast carrier mobilities are identified from the extraction current transient. The equilibrium carrier concentration is also estimated for each of the blend films. The product of the slow carrier mobility and equilibrium concentration spreading two orders of magnitude can be used to estimate the short circuit current density. A good agreement between the estimated and measured short circuit current density is obtained with the accuracy reliant on the estimation of the slowest carrier mobility. This simplistic approach will be very useful to predict the short circuit current density for devices based on new materials. © 2012 Springer-Verlag.
Jones DJ, Purushothaman B, Ji S, et al., 2012, Synthesis of electron-poor hexa-peri-hexabenzocoronenes., Chem Commun (Camb), Vol: 48, Pages: 8066-8068
The oxidative cyclodehydrogenation of electron-poor arenes was achieved using DDQ-CF(3)SO(3)H resulting in hexa-peri-hexabenzocoronenes with electron withdrawing Br, F and CF(3) groups. This method will lead to their expansion into a new class of electron transport materials.
Krenske EH, Agopcan S, Aviyente V, et al., 2012, Causation in a cascade: the origins of selectivities in intramolecular nitrone cycloadditions., J Am Chem Soc, Vol: 134, Pages: 12010-12015
The factors controlling chemo-, regio-, and stereoselectivity in a cascade of reactions starting from a bis(cyanoalkenyl)oxime and proceeding via nitrone cycloadditions have been unraveled through a series of density functional theory calculations with several different functionals. Both kinetic and thermodynamic control of the reaction cascade are important, depending upon the conditions. Kinetic control was analyzed by the distortion/interaction model and found to be dictated by differences in distortions of the cycloaddends in the transition states. A new mechanism competing with that originally proposed in the application of these reactions to the histrionicotoxin synthesis was discovered in these studies.
Ren S, Yan C, Vak D, et al., 2012, Solution processable monosubstituted hexa-peri-hexabenzocoronene self-assembling dyes, Advanced Functional Materials, Vol: 22, Pages: 2015-2026, ISSN: 1616-301X
Molecular organization behavior and visible light absorption ability are important factors for organic materials to be used in efficient bulk heterojunction solar cells applications. In this context, a series of monosubstituted fluorenyl hexa-peri-hexabenzocoronene (FHBC) are synthesized with the aim to combine the self-association property of the FHBC unit with broadened light absorption of a small molecule organic dye, bisthienylbenzothiadiazole (TBT). Optical and electrochemical properties of the FHBC compounds vary according to their structures. Introduction of a TBT unit into the FHBC system broadens the absorption. All of the FHBC compounds show strong π-π intermolecular association in solution. X-ray scattering measurements on thermally extruded filaments and thin films showed ordered alignment of these compounds in the solid state. In atomic force microscopy experiments, nanoscale phase separation is observed in thin films of FHBC and fullerene derivative blends. Solar cell devices with these compounds as donors are fabricated. FHBC compounds with the TBT unit show higher short circuit current while the high open circuit voltages are maintained. With C 60 derivative as acceptor, power conversion efficiency of 1.12% is achieved in the unoptimized solar cell devices under simulated solar irradiation. The efficiency was further improved to 1.64% when C 70 derivative was used as the acceptor. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Daeneke T, Mozer AJ, Kwon TH, et al., 2012, Dye regeneration and charge recombination in dye-sensitized solar cells with ferrocene derivatives as redox mediators, Energy and Environmental Science, Vol: 5, Pages: 7090-7099, ISSN: 1754-5692
Ferrocene compounds are promising redox shuttles for application in dye-sensitized solar cells (DSCs). Chemical modification of the cyclopentadienyl rings is easily achievable affording almost unlimited variation of the redox properties. This allows fine-tuning of the driving force for dye-regeneration and optimization of the energy conversion efficiency of DSCs. Herein, six ferrocene derivatives have been chosen for investigation which cover the large redox potential range of 0.85 V, by virtue of simple alkylation and halogenation of the cyclopentadienyl ring, and enable improved matching of the energy levels of the sensitizer and the electrolyte. Although the focus of this work was to examine the effect of the redox potential on charge transfer processes, DSCs were fabricated which achieved high energy conversion efficiencies of over 5%. Charge transfer reactions were studied to reveal the dependence of the dye regeneration rate, recombination losses and recombination pathways on the reaction driving force. An increase in redox potential led to a higher efficiency due to higher open circuit potentials until a threshold is reached. At this threshold, the driving force for dye regeneration (18 kJ mol -1, ΔE = 0.19 V) becomes too small for efficient device operation, leading to rapid recombination between the oxidized dye and electrons in the TiO2 conduction band. As a result of this work guidelines can be formulated to aid the selection of redox couples for a particular sensitizer in order to maximize the utilization of incident solar energy. © 2012 The Royal Society of Chemistry.
Seyler H, Purushothaman B, Jones DJ, et al., 2012, Hexa-peri-hexabenzocoronene in organic electronics, Pure and Applied Chemistry, Vol: 84, Pages: 1047-1067, ISSN: 0033-4545
Polycyclic aromatic hydrocarbons (PAHs) are in a class of functional organic compounds with increasing importance in organic electronics. Their tunable photophysical properties and typically strong intermolecular associations make them ideal materials in applications where control of charge mobility is essential. Hexa-peri-hexabenzocoronene (HBC) is a disc-shaped PAH that self-associates into columnar stacks through strong lπ-lΠ interactions. By decorating the periphery of the HBC molecule with various substituents, a range of properties and functions can be obtained including solution processability, liquid crystallinity, and semiconductivity. In this review article, the synthesis, properties, and functions of HBC derivatives are presented with focus on work published in the last five years. © 2012 IUPAC.
Colsmann A, Reinhard M, Kwon TH, et al., 2012, Inverted semi-transparent organic solar cells with spray coated, surfactant free polymer top-electrodes, Solar Energy Materials and Solar Cells, Vol: 98, Pages: 118-123, ISSN: 0927-0248
Depositing a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) buffer layer or top-electrode from aqueous solution on a non-polar active layer in inverted organic solar cells is commonly considered a very challenging task. In this work we utilize spray deposited PEDOT:PSS seeds to effectively reduce the surface free energy atop the active layer in poly-hexylthiophene polymer solar cells before applying a PEDOT:PSS top-electrode. Though aqueous PEDOT:PSS is repelled from non-polar surfaces, very small droplets can adhere to the surface. The distribution of the sprayed PEDOT:PSS droplets can be controlled via the substrate temperature and the material flow rate. The less time the droplets have to contract along the surface before drying, the better is the surface seed coverage and the more homogenous is the formation of a subsequently deposited PEDOT:PSS electrode. The respective solar cells are semi-transparent and exhibit an overall power conversion efficiency η≈2%. © 2011 Elsevier B.V. All rights reserved.
Seyler H, Jones DJ, Holmes AB, et al., 2012, Continuous flow synthesis of conjugated polymers., Chem Commun (Camb), Vol: 48, Pages: 1598-1600
A selection of conjugated polymers, widely studied in organic electronics, was synthesised using continuous flow methodology. As a result of superior heat transfer and reagent control, excellent polymer molecular mass distributions were achieved in significantly reduced reaction times compared to conventional batch reactions.
Krenske EH, Davison EC, Forbes IT, et al., 2012, Reverse cope elimination of hydroxylamines and alkenes or alkynes: theoretical investigation of tether length and substituent effects., J Am Chem Soc, Vol: 134, Pages: 2434-2441
Quantum mechanical calculations have been used to study the intramolecular additions of hydroxylamines to alkenes and alkynes ("reverse Cope eliminations"). In intermolecular reverse Cope eliminations, alkynes are more reactive than alkenes. However, competition experiments have shown that tethering the hydroxylamine to the alkene or alkyne can reverse the reactivity order from that normally observed. The exact outcome depends on the length of the tether. In agreement with experiment, a range of density functional theory methods and CBS-QB3 calculations predict that the activation energies for intramolecular reverse Cope eliminations follow the order 6-exo-dig < 5-exo-trig < 5-exo-dig ≈ 7-exo-dig. The order of the barriers for the 5-, 6-, and 7-exo-dig reactions of alkynes arises mainly from differences in tether strain in the transition states (TSs), but is also influenced by the TS interaction between the hydroxylamine and alkyne. Cyclization onto an alkene in the 5-exo-trig fashion incurs slightly less tether strain than a 6-exo-dig alkyne cyclization, but its activation energy is higher because the hydroxylamine fragment must distort more before the TS is reached. If the alkene terminus is substituted with two methyl groups, the barrier becomes so much higher that it is also disfavored compared to the 5- and 7-exo-dig cyclizations.
Maniam S, Holmes AB, Krstina J, et al., 2011, Supercritical carbon dioxide as a solvent for deposition of a tailored dye in dye sensitized solar cells, Green Chemistry, Vol: 13, Pages: 3329-3332, ISSN: 1463-9262
We report a new technique whereby dyes can be deposited onto metal oxide surfaces using supercritical carbon dioxide (scCO2) for use in solar cell applications. This process eliminates the need for hazardous organic solvents and waste solvents generated during the dyeing process. The solubility of a perylene anhydride dye in scCO2 is enhanced by the incorporation of fluorinated alkyl subsituents and the use of masked carboxylic binding groups. This allows fast deposition of the dye onto the TiO2 photoanode, resulting in efficient photovoltaic performance. The unreacted dye is then easily recovered in a solid form after the deposition process by venting the carbon dioxide. © 2011 The Royal Society of Chemistry.
Holmes AB, Jones DJ, Wong WWH, et al., 2011, Synthesis of conjugated materials for light emission and light harvesting, 242nd National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Holmes AB, Jones DJ, Kwon TH, et al., 2011, Progress in the development of conjugated materials for organic and dye-sensitized dye solar cells, ISSN: 0065-7727
In this paper advances in the synthesis of conjugated organic and polymeric materials for application as the active layer in organic (OPV) and dye-sensitized solar cells (DSC) will be reported. A variety of materials ranging from solution processable hexabenzocoronenes to donor-acceptor organic dyes for DSC with alternative electrolyte materials have been studied. As part of the Victorian Organic Solar Cells Consortium (VICOSC) a progress report will be given on scale-up of materials synthesis and deposition processes.
Kumar RJ, MacDonald JM, Singh TB, et al., 2011, Hierarchical self-assembly of semiconductor functionalized peptide α-helices and optoelectronic properties., J Am Chem Soc, Vol: 133, Pages: 8564-8573
To determine the ability of semiconductors templated by α-helical polypeptides to form higher order structures and the charge carrier properties of the supramolecular assemblies, L-lysine was functionalized with a sexithiophene organic semiconductor unit via iterative Suzuki coupling and the click reaction. The resultant amino acid was incorporated into a homopolypeptide by ring-opening polymerization of an amino acid N-carboxyanhydride. Spectroscopic investigation of the polypeptide revealed that it adopted an α-helical secondary structure in organic solvents that underwent hierarchical self-assembly to form higher order structures. In cyclohexane, the polymer formed organogels at 2% (w/v). Organic photovoltaic and organic field effect transistor devices were fabricated by deposition of the PCBM blended active layer from chlorobenzene at concentrations shown to induce self-assembly of the polymer. Compared with control compounds, these devices showed significantly greater hole mobility, short circuit current, and efficiency. This work establishes the potential of this previously unreported bioinspired motif to increase device performance.
Kwon T-H, Armel V, Nattestad A, et al., 2011, Dithienothiophene (DTT)-based dyes for dye-sensitized solar cells: synthesis of 2,6-dibromo-DTT., J Org Chem, Vol: 76, Pages: 4088-4093
A one-pot synthesis of 2,6-dibromodithieno[3,2-b;2',3'-d]thiophene (dibromo-DTT, 4) was developed. A key step was bromodecarboxylation of DTT-2,6-dicarboxylic acid, obtained by saponification of the diester 1. The donor-acceptor dye DAHTDTT (13), based on a central 2,6-bis[2'-(3'-hexylthienyl)]dithieno[3,2-b;2',3'-d]thiophene core (9), was prepared and incorporated in a dye-sensitized solar cell (DSC), which exhibited an energy conversion efficiency of 7.3% with V(oc) of 697 mV, J(sc) of 14.4 mA/cm(2), and ff of 0.73 at 1 sun.
Wong WWH, Ma C-Q, Pisula W, et al., 2011, Fluorenyl hexa-peri-hexabenzocoronene-dendritic oligothiophene hybrid materials: synthesis, photophysical properties, self-association behaviour and device performance., Chemistry, Vol: 17, Pages: 5549-5560
Apart from molecular properties, intermolecular forces play a vital role in defining the performance of organic electronic devices. This is particularly relevant in bulk heterojunction (BHJ) solar cells in which the arrangement of electron-donor and -acceptor materials into distinct crystalline phases of ideal size and distribution can lead to better power conversion efficiencies. In this study, a series of fluorenyl hexa-peri-hexabenzocoronenes (FHBC) decorated with thiophene dendrons (DOT) of variable size was obtained by using a convergent synthetic approach. With such variety of molecular sizes and shapes in hand, the objective of this study is to highlight the relationships between molecular properties, bulk properties and device performance. Correlations between π-π stacking ability and dendrimer generation were established from self-organisation studies in solution and solid state. The synergistic combination of molecular organisation at the nanoscale and photophysical characteristics derived from the FHBC and DOT moieties leads to a notable improvement of the photovoltaic performance.
Seyler H, Wong WWH, Jones DJ, et al., 2011, Continuous flow synthesis of fullerene derivatives., J Org Chem, Vol: 76, Pages: 3551-3556
Various fullerene-based electron acceptor materials for organic photovoltaic applications were prepared via [3+2] and [4+2] cycloadditions using a continuous flow approach. The 1,3-dipolar cycloaddition of the tosylhydrazone precursor and the Diels-Alder cycloaddition of indene to either C(60) or C(70) under conventional batch reaction conditions were translated to the continuous flow process. By varying the residence time, temperature, and equivalents of cycloaddition reagent, significant improvements in yields and reaction times were achieved over conventional batch processes.
Krenske EH, Houk KN, Holmes AB, et al., 2011, Entropy versus tether strain effects on rates of intramolecular 1,3-dipolar cycloadditions of N-alkenylnitrones, Tetrahedron Letters, Vol: 52, Pages: 2181-2184, ISSN: 0040-4039
Intramolecular 1,3-dipolar cycloadditions of two N-alkenylnitrones are studied by means of density functional theory calculations. Cycloaddition of an acyclic 4-hexenylnitrone led to the expected isoxazolidine in 46% yield, but a 4-cycloheptenylnitrone did not react. Calculations of the transition states for cycloaddition indicate that although the cycloheptenyl nitrone has a more favorable activation entropy, the strain associated with distortion of the tethering groups into the required boat conformation disfavors the reaction of the cyclic substrate over the acyclic substrate by 8.7 kcal/mol. © 2010 Elsevier Ltd. All rights reserved.
Daeneke T, Kwon TH, Holmes AB, et al., 2011, High-efficiency dye-sensitized solar cells with ferrocene-based electrolytes, Nature Chemistry, Vol: 3, Pages: 211-215, ISSN: 1755-4330
Dye-sensitized solar cells based on iodide/triiodide (I-/I 3-) electrolytes are viable low-cost alternatives to conventional silicon solar cells. However, as well as providing record efficiencies of up to 12.0%, the use of I-/I3- in such solar cells also brings about certain limitations that stem from its corrosive nature and complex two-electron redox chemistry. Alternative redox mediators have been investigated, but these generally fall well short of matching the performance of conventional I-/I3- electrolytes. Here, we report energy conversion efficiencies of 7.5% (simulated sunlight, AM1.5, 1,000 W m-2) for dye-sensitized solar cells combining the archetypal ferrocene/ferrocenium (Fc/Fc+) single-electron redox couple with a novel metal-free organic donor-acceptor sensitizer (Carbz-PAHTDTT). These Fc/Fc+-based devices exceed the efficiency achieved for devices prepared using I-/I3- electrolytes under comparable conditions, revealing the great potential of ferrocene-based electrolytes in future dye-sensitized solar cells applications. This improvement results from a more favourable matching of the redox potential of the ferrocene couple with that of the new donor-acceptor sensitizer. © 2011 Macmillan Publishers Limited. All rights reserved.
Fong HH, Lee J-K, Lim Y-F, et al., 2011, Orthogonal processing and patterning enabled by highly fluorinated light-emitting polymers., Adv Mater, Vol: 23, Pages: 735-739
D'Souza AM, Spiccia N, Basutto J, et al., 2011, 1,3-Dipolar cycloaddition-decarboxylation reactions of an azomethine ylide with isatoic anhydrides: formation of novel benzodiazepinones., Org Lett, Vol: 13, Pages: 486-489
A nonstabilized azomethine ylide reacts with a wide range of substituted isatoic anhydrides to afford novel 1,3-benzodiazepin-5-one derivatives, which are generally isolated in high yield. The transformations involve 1,3-dipolar cycloaddition reactions of the ylide with the anhydrides to give transient, and in a representative case spectroscopically observable, oxazolidine intermediates that undergo ring-opening-decarboxylation-ring-closing reaction cascades to yield the 1,3-benzodiazepin-5-one products.
Keyworth CW, Chan KL, Labram JG, et al., 2011, The tuning of the energy levels of dibenzosilole copolymers and applications in organic electronics, Journal of Materials Chemistry, Vol: 21, Pages: 11800-11814, ISSN: 0959-9428
An understanding of the structure-function relationships of conjugated polymers is an invaluable resource for the successful design of new materials for use in organic electronics. To this end, we report the synthesis, characterisation and optoelectronic properties of a range of new alternating copolymers of dibenzosilole. Suzuki polycondensation reactions were used to afford a series of eight conjugated materials by the respective combination of either a 3,6- or 2,7-linked 9,9-dioctyldibenzosilole with 3,6-linked-N-octylcarbazole, triarylamine, oxadiazole and triazole monomers. The copolymers were fully characterised using 1H, 13C{1H} NMR spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The photophysical properties were determined using UV-Vis spectroscopy, photoluminescence (PL) measurements, cyclic voltammetry (CV) and photoelectron emission spectroscopy in air (PESA). The spectroscopic and electrochemical measurements were used to determine the materials' HOMO and LUMO energies and the values were correlated with the copolymer composition and structure. A selection of the copolymers (P4, P5 and P8) were evaluated as the active layer within single-layer polymer light emitting diodes (PLEDs), with the configuration: glass/ITO/PEDOT:PSS/emissive layer/Ba/Al, which gave low intensity electroluminescence. The selected copolymers were also evaluated as the organic semiconductor in bottom-gate, bottom-contact organic field effect transistors (OFETs). The best performing devices gave a maximum mobility of 3 [times] 10-4 cm2 V-1 s-1 and on/off current ratios of 105.
Wong WWH, Vak D, Singh TB, et al., 2010, Ambipolar Hexa-peri-hexabenzocoronene-fullerene hybrid materials, Organic Letters, Vol: 12, Pages: 5000-5003, ISSN: 1523-7060
A new class of self-assembling hexa-peri-hexbenzocoronene (HBC)-fullerene hybrid materials has been synthesized and characterized. Photoluminescence experiments indicate that energy transfer processes can be tuned in these donor-acceptor systems by varying the length and nature of the linker group. In preliminary device testing, ambipolar charge transport behavior is observed in organic field effect transistors, while single active component organic photovoltaic devices consisting of these materials achieved a maximum external quantum efficiency of 30%. © 2010 American Chemical Society.
Palmieri M, Nowell CJ, Condron M, et al., 2010, Analysis of cellular phosphatidylinositol (3,4,5)-trisphosphate levels and distribution using confocal fluorescent microscopy., Anal Biochem, Vol: 406, Pages: 41-50
We have developed an immunocytochemistry method for the semiquantitative detection of phosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P3) at the cell plasma membrane. This protocol combines the use of a glutathione S-transferase-tagged pleckstrin homology (PH) domain of the general phosphoinositides-1 receptor (GST-GRP1PH) with fluorescence confocal microscopy and image segmentation using cell mask software analysis. This methodology allows the analysis of PI(3,4,5)P3 subcellular distribution in resting and epidermal growth factor (EGF)-stimulated HEK293T cells and in LIM1215 (wild-type phosphoinositide 3-kinase (PI3K)) and LIM2550 (H1047R mutation in PI3K catalytic domain) colonic carcinoma cells. Formation of PI(3,4,5)P3 was observed 5min following EGF stimulation and resulted in an increase of the membrane/cytoplasm fluorescence ratio from 1.03 to 1.53 for HEK293T cells and from 2.2 to 3.3 for LIM1215 cells. Resting LIM2550 cells stained with GST-GRP1PH had an elevated membrane/cytoplasm fluorescence ratio of 9.8, suggesting constitutive PI3K activation. The increase in the membrane/cytoplasm fluorescent ratio was inhibited in a concentration-dependent manner by the PI3K inhibitor LY294002. This cellular confocal imaging assay can be used to directly assess the effects of PI3K mutations in cancer cell lines and to determine the potential specificity and effectiveness of PI3K inhibitors in cancer cells.
Brasholz M, Macdonald JM, Saubern S, et al., 2010, A gram-scale batch and flow total synthesis of perhydrohistrionicotoxin., Chemistry, Vol: 16, Pages: 11471-11480
The total synthesis of the spiropiperidine alkaloid (-)-perhydrohistrionicotoxin (perhydro-HTX) 2 has been accomplished on a gram scale by employing both conventional batch chemistry as well as microreactor techniques. (S)-(-)-6-Pentyltetrahydro-pyran-2-one 8 underwent nucleophilic ring opening to afford the alcohol 10, which was elaborated to the nitrone 13. Protection of the nitrone as the 1,3-adduct of styrene and side-chain extension to the unsaturated nitrile afforded a precursor 17, which underwent dipolar cycloreversion and 1,3-dipolar cycloaddition to give the core spirocyclic precursor 18 that was converted into perhydro-HTX 2. The principal steps to the spirocycle 18 have successfully been transferred into flow mode by using different types of microreactors and in a telescoped fashion, allowing for a more rapid access to the histrionicotoxins and their analogues by continuous processing.
Wong WWH, Khoury T, Vak D, et al., 2010, A porphyrin-hexa-peri-hexabenzocoronene-porphyrin triad: Synthesis, photophysical properties and performance in a photovoltaic device, Journal of Materials Chemistry, Vol: 20, Pages: 7005-7014, ISSN: 0959-9428
Hexa-peri-hexabenzocoronene (HBC) is a discotic polycyclic aromatic hydrocarbon with good charge transport characteristics while the light harvesting property of porphyrins is well-known. In order to take advantage of the properties of both materials, a porphyrin-hexa-peri-hexabenzocoronene- porphyrin triad 6 was synthesised for the first time. In photoluminescence studies, the emission from the higher energy HBC unit was completely quenched by the porphyrin unit indicating efficient energy transfer. This novel hybrid material 6 was tested in bulk heterojunction photovoltaic devices reaching a power conversion efficiency of 1.2%. © 2010 The Royal Society of Chemistry.
Brasholz M, Johnson BA, Macdonald JM, et al., 2010, Flow synthesis of tricyclic spiropiperidines as building blocks for the histrionicotoxin family of alkaloids, Tetrahedron, Vol: 66, Pages: 6445-6449, ISSN: 0040-4020
A domino cyclization reaction of the bis-unsaturated ketone 3 with hydroxylamine proceeds with good yield and high stereoselectivity, in a flow reactor system. The tricyclic spiropiperidine products 5 and 2 obtained are valuable building blocks for the synthesis of analogues of the histrionicotoxin alkaloids. © 2010 Elsevier Ltd.
Wong LSM, Turner KA, White JM, et al., 2010, Asymmetric synthesis of a hydroxylated nine-membered lactone from tartaric acid using the claisen rearrangement, Australian Journal of Chemistry, Vol: 63, Pages: 529-532, ISSN: 0004-9425
The synthesis of a hydroxylated vinyl-appended lactone, in five synthetic steps from tartaric acid, is reported. The C2-symmetrical bis-vinyl diol 12 was converted into the ketene acetal 14 via methylenation of the cyclic carbonate 13 or thermal elimination of benzeneselenenic acid from the selenoxide 17. In both cases, the in situ generated ketene acetal 14 underwent spontaneous Claisen rearrangement to give the nine-membered lactone (+)-15. Lactones of this type are potentially advanced precursors to simplified eleutherobin analogues or other medium-ring lactone natural products. © 2010 CSIRO.
Saubern S, MacDonald JM, Ryan JH, et al., 2010, Tricyclic-isoxazolidine analogues via intramolecular 1,3-dipolar cycloaddition reactions of nitrones., TETRAHEDRON, Vol: 66, Pages: 2761-2767
Wong WWH, Birendra Singh T, Vak D, et al., 2010, Solution processable fluorenyl hexa-peri-hexabenzocoronenes in organic field-effect transistors and solar cells, Advanced Functional Materials, Vol: 20, Pages: 927-938, ISSN: 1616-301X
The organization of organic semiconductor molecules in the active layer of organic electronic devices has important consequences to overall device performance. This is due to the fact that molecular organization directly affects charge carrier mobility of the material. Organic field-effect transistor (OFET) performance is driven by high charge carrier mobility while bulk heterojunction (BHJ) solar cells require balanced hole and electron transport. By investigating the properties and device performance of three structural variations of the fluorenyl hexa-peri-hexabenzocoronene (FHBC) material, the importance of molecular organization to device performance was highlighted. It is clear from 1H NMR and 2D wide-angle X-ray scattering (2D WAXS) experiments that the sterically demanding 9,9-dioctylfluorene groups are preventing π-π intermolecular contact in the hexakis-substituted FHBC 4. For bis-substituted FHBC compounds S and 6, π-π intermolecular contact was observed in solution and hexagonal columnar ordering was observed in solid state. Furthermore, in atomic force microscopy (AFM) experiments, nanoscale phase separation was observed in thin films of FHBC and [6,6]phenyl-C61-butyric acid methyl ester (FC61BM) blends. The differences in molecular and bulk structural features were found to correlate with OFET and BHJ solar cell performance. Poor OFET and BHJ solar cells devices were obtained for FHBC compound 4 while compounds 5 and 6 gave excellent devices. In particular, the field-effect mobility of FHBC 6, deposited by spincasting, reached 2.8 x 10 3Cm2 V-1 s and a power conversion efficiency of 1.5% was recorded for the BHJ solar cell containing FHBC 6 and PC 61BM. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.
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