Publications
552 results found
Ley SV, Ramarao C, Gordon RS, et al., 2002, Polyurea-encapsulated palladium(II) acetate: a robust and recyclable catalyst for use in conventional and supercritical media., Chem Commun (Camb), Pages: 1134-1135, ISSN: 1359-7345
Palladium(II) acetate microencapsulated in polyurea (MC-[Pd]) is an economical and versatile heterogeneous catalyst for a range of phosphine-free cross-coupling reactions in both conventional solvents and supercritical carbon dioxide (scCO2); the catalyst can be recovered by a simple filtration and recycled up to four times.
Dini D, Martin RE, Holmes AB, 2002, Anodic and cathodic electrochemically generated chemiluminescence in conjugated polymers, Advanced Functional Materials, Vol: 12, Pages: 299-306, ISSN: 1616-301X
In the present contribution, we show that long-lived electrochemically generated chemiluminescence (ECL) from conjugated polymers can be achieved in both anodic and cathodic polarizations of poly[2-(2′-ethylethoxy)-5-methoxy 1,4-phenylene vinylene] (MEH-PPV), when the appropriate electrochemical conditions are adopted and an adequate degree of purity for the active polymer, solvent, and supporting electrolyte is achieved. The qunatum efficiency is generally higher during the anodic polarization of MEH-PPV, whereas the ECL vs. time profile depends on the nature of the supporting electrolyte. Such findings led to the conclusion that the kinetics of the doping/undoping processes in MEH-PPV represents a crucial factor in determining the emissive properties of the conjugated polymer. A comparison of the ECL emission from analogous polymeric systems, namely poly[2,5-bis-(triethoxymethoxy)-1,4-phenylene vinylene] (BTEM-PPV) and poly[2,3-dibutoxy-1,4-phenylene vinylene] (DB-PPV), is also reported.
Berst F, Ladlow M, Holmes AB, 2002, Solid-phase synthesis of apicidin A and a cyclic tetrapeptoid analogue., Chem Commun (Camb), Pages: 508-509, ISSN: 1359-7345
The solid-phase synthesis of the antiprotozoal cyclic tetrapeptide apicidin A is reported and its synthetic accessibility is contrasted with that of a structurally similar reduced cyclic tetrapeptoid analogue.
Anderson EA, Davidson JEP, Harrison JR, et al., 2002, Synthesis of medium-ring lactones via tandem methylenation/Claisen rearrangement of cyclic carbonates, Tetrahedron, Vol: 58, Pages: 1943-1971, ISSN: 0040-4020
The conversion of vinyl-substituted 6- and 7-membered cyclic carbonates into 8- and 9-membered medium-ring lactones has been achieved in good yield using dimethyltitanocene in toluene at reflux. The reaction proceeds by initial formation of a ketene acetal which undergoes subsequent in situ Claisen rearrangement to provide the corresponding lactones. The preparation of the cyclic carbonates is carried out under basic conditions and hence this methodology complements our existing selenium-based methodology for the synthesis of medium-ring lactones. © 2002 Published by Elsevier Science Ltd.
Lim ZY, Thuring JW, Holmes AB, et al., 2002, Synthesis and biological evaluation of a PtdIns(4,5)P<inf>2</inf>and a phosphatidic acid affinity matrix, Journal of the Chemical Society. Perkin Transactions 1, Vol: 2, Pages: 1067-1075, ISSN: 1472-7781
Analogues of dipalmitoyl phosphatidic acid (PA), dilauroyl PA and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] were synthesised and immobilised onto a solid support, Affi-Gel 10. Using them as affinity matrices, a number of known proteins as well as a set of novel proteins were found to bind specifically to PA. © 2002 The Royal Society of Chemistry.
Davison EC, Fox ME, Holmes AB, et al., 2002, Nitrone dipolar cycloaddition routes to piperidines and indolizidines, Journal of the Chemical Society. Perkin Transactions 1, Vol: 2, Pages: 1494-1514, ISSN: 1472-7781
An intramolecular hydroxylamine-alkyne cyclisation is used for the enantioselective synthesis of the cyclic nitrones 36 and 44. We have demonstrated the use of a novel nitrone protection strategy by cycloaddition of styrene to the cyclic nitrone 44 in the synthesis of the spirocyclic core of the histrionicotoxin family of alkaloids. Deprotection by dipolar cycloreversion of the styrene adduct (the bicyclic isoxazolidine 39) and in situ intramolecular dipolar cycloaddition of a pendant (Z)-α,β-unsaturated nitrile to the intermediate nitrone 50 gave the isoxazolidine 51 in high yield with a surprising degree of regioselectivity compared with the corresponding (Z)-enyne 36. The method is amenable to the synthesis of both enantiomers 51 and 62 of the tricyclic core structure which can be converted by way of the common intermediates (e.g. 53 and ent-53) respectively into the natural configuration of alkaloids (−)-histrionicotoxin 1 and (−)-histrionicotoxin 235A 65 as well as the unnatural (+)-histrionicotoxin 63. © 2002 The Royal Society of Chemistry.
Rees ID, Robinson KL, Holmes AB, et al., 2002, Recent developments in light-emitting polymers, MRS Bulletin, Vol: 27, Pages: 451-455, ISSN: 0883-7694
Conjugated light-emitting polymers (LEPs) have real potential to serve as the active layer in a new generation of emissive displays. Emerging as lead candidates for first-generation displays are poly(1,4-phenylene vinylene)s (PPVs) and poly(9,9-dialkylfluorene)s, as well as other polyaromatic materials. The poly(fluorene)s are at present the most commercially developed of these LEP materials for red-green-blue (RGB) applications. The low power consumption of LEP devices in general makes them particularly suited to mobile applications. Combining solution-processable emissive polymers with direct-patterning methods such as ink-jet printing will lead to the possibility of low-cost, high-resolution displays. The synthesis and properties of PPVs and poly(9,9-dialkylfluorene)s are briefly reviewed in this article, with a major focus on recent developments.
Holmes AB, Bond AD, Davies JE, et al., 2002, Design of luminescent polymers for leds, Materials Research Society Symposium - Proceedings, Vol: 708, Pages: 185-195, ISSN: 0272-9172
A 2,3-dibutoxy-1,4-phenylenevinylene comonomer was incorporated into a distyrylbenzene derivative 11. Novel 1,2-disubstituted-3,6-dibromobenzene comonomers 15 and 18 were prepared by directed metallation. Copolymerization of 11 with a 9,9-dioctylfluorene-2,7-diboronate ester 1 yielded a green fluorescent polymer with copolymerization of 15 and 18 with the 9,9-dihexylfluorene-2,7-diboronate 22 afforded promising blue fluorescent polymers 23 and 24 respectively.
Luscombe CK, Huck WTS, Holmes AB, et al., 2002, Patterned deposition from compressed carbon dioxide, Pages: 1-6, ISSN: 0272-9172
Compressed CO2 is employed as the solvent for the deposition of polymers onto patterned surfaces created by a lithographic technique. This deposition technique should have wide applicability in the deposition of organic and polymeric materials for optoelectronic devices. The advantage of controlled deposition confers a further benefit in the control of the patterned surface. In a specific example a perfluorinated polymer was dissolved in liquid carbon dioxide. The polymer solution was deposited by use of a nozzle onto a pre-patterned surface. The resulting polymer film showed a clear image of the original pattern as measured by optical microscopy. © 2003 Materials Research Society.
Rose NGW, Blaskovich MA, Evindar G, et al., 2002, Preparation of 1-[N-benzyloxycarbonyl-(1S)-1-amino-2-oxoethyl]-4-methyl-2,6,7-trioxabicyclo[2.2.2] octane: [Carbamic acid, [1-(4-methyl-2,6,7-trioxabicyclo[2.2.2]oct-1-yl)-2-oxoethyl]-, phenylmethyl ester, (S)-], Organic Syntheses, Vol: 79, ISSN: 0078-6209
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- Citations: 16
Bao Z, Bulovic V, Holmes AB, et al., 2002, Electroactive organic materials, MRS Bulletin, Vol: 27, Pages: 441-445, ISSN: 0883-7694
This brief article describes the content of the June 2002 issue of MRS Bulletin focusing on Electroactive Organic Materials. These materials are now being considered as the active components in displays, electronic circuits, solar cells, chemical and biological sensors, actuators, lasers, memory elements, and fuel cells. The flexibility of their molecular design and synthesis makes it possible to fine-tune the physical properties and material structure of organic solids to meet the requirements of technologically significant applications. In contrast to inorganic materials, active organic thin films can be deposited at much lower substrate temperatures (less than 120°C) in low-vacuum or atmospheric-pressure environments. It has been demonstrated that low-cost deposition techniques such as solution spin-coating, casting, and even printing can be used for the deposition of solution-soluble organic materials. These processing advantages, together with the natural abundance of organic solids, make electroactive organic materials attractive for large-area and low-cost applications.
Sano T, Tuan CS, Martin RE, et al., 2002, Multi-layer polymer light-emitting diodes with 2,3-dialkoxy-p-phenylene vinylene and its blends, Journal of Photopolymer Science and Technology, Vol: 15, Pages: 253-258, ISSN: 0914-9244
A green-fluorescent polymer, poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV), was synthesized and used in electroluminescent (EL) devices. By introducing a small molecular electron-transport layer in a device, the EL efficiencies were improved up to 1.26 cd/A. A polymer-blend with DB-PPV and poly(9,9-dioctylfluorene) (PF8) was also examined. The EL peak wavelength was blue-shifted to 503 nm and the EL efficiencies were improved in the polymer-blend device. A layered structure and a polymer-blend system both have shown contribution to the improvements of the polymer light-emitting diodes using DB-PPV.
Frey J, Bond AD, Holmes AB, 2002, Improved synthesis of dithieno[3,2-b:2’,3’-d]thiophene (DTT) and derivatives for cross coupling, Chemical Communications, Vol: 2, Pages: 2424-2425, ISSN: 1359-7345
An improved synthesis of dithieno[3,2-b:2’,3’-d]thiophene (DTT) and its 2,6- and 3,5-dibromo derivatives has been devised; Stille cross coupling of 2,5-(bistrimethylstannyl)-DTT afforded the oligomer 12. © 2002 The Royal Society of Chemistry.
Tormo J, Fu GC, Thuring JW, et al., 2002, Tributylstannane (Bu<inf>3</inf>SnH)-catalyzed barton-mccombie deoxygenation of alcohols: 3-deoxy-1,2:5,6-bis-O-(1-methylethylidene)-Į-D-ribo-hexofuranose: [ α-D-ribo-Hexofuranose, 3-deoxy-1,2:5,6-bis-O-(1-methylethylidene)- ], Organic Syntheses, Vol: 78, ISSN: 0078-6209
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- Citations: 8
Meijere AD, Kozhushkov SI, Späth T, et al., 2002, Bicyclopropylidene: [ Cyclopropane, cyclopropylidene ], Organic Syntheses, Vol: 78, ISSN: 0078-6209
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- Citations: 47
Holmes AB, Sano T, Fischmeister C, et al., 2002, A new family of polyfluorene copolymers for light emitting devices, Proceedings of SPIE - The International Society for Optical Engineering, Vol: 4464, Pages: 42-48, ISSN: 0277-786X
Further routes have been developed for the synthesis of 1,4-bishalomethylbenzene derivatives for Gilch dehydrohalogenation polycondensation. Poly(2,3-dibutoxy-1,4-phenylenevinylene) is a prototypical conjugated polymer which is thought to derive its high PL solid state fluorescence efficiency from the sterically twisted backbone and devices carrying this polymer have been further evaluated. Distyrylbenzene derivative carrying the structural feature of a 2,3-dibutoxy substitution pattern on the central ring have been prepared. One in particular has been copolymerized with a 9,9-dialkyl-fluorene-2,7-diboronate ester. The resulting conjugated polymer shows a good green emission maximum in an electroluminescent device.
Davison EC, Fox ME, Holmes AB, et al., 2002, Nitrone dipolar cycloaddition routes to piperidines and indolizidines. Part 9. Formal synthesis of (-)-pinidine and total synthesis of (+)-histrionicotoxin, (-)-histrionicotoxin and (-)-histrionicotoxin 235A, J. Chem. Soc., Perkins Trans, Pages: 1494-1514
Krugmann S, Anderson KE, Ridley SH, et al., 2002, Identification of ARAP3, a Novel PI3K Effector Regulating both Arf and Rho GTPases, by Selective Capture on Phosphoinositide Affinity Matrices, Mol. Cell, Pages: 95-108
Gordon RS, Holmes AB, 2002, Palladium-mediated Cross-coupling Reactions with Supported Reagents in Supercritical Carbon Dioxide, Chem. Commun, Pages: 640-641
Stamp LM, Mang SA, Holmes AB, et al., 2001, Polymer supported chromium porphyrin as catalyst for polycarbonate formation in supercritical carbon dioxide., Chem Commun (Camb), Pages: 2502-2503, ISSN: 1359-7345
A new polymer-supported chromium porphyrin has been prepared and fully characterised; its catalytic activity and recyclability were investigated for the ring-opening copolymerisation of 1,2-cyclohexene oxide (CHO) and carbon dioxide (CO2).
Fischmeister C, Geneste F, Holmes AB, et al., 2001, Synthesis of new building blocks for light emitting polymers, ISSN: 0272-9172
The synthesis of poly(2,3-dibutoxy-1,4-phenylene vinylene) (DB-PPV) has allowed the study of this material as the active layer in a multiple layer device using a composite combination of polymer and Alq3 with an oxadiazole as electron injection/transport layers. The luminous efficiency of the resulting device was significantly improved as a result of this combination of transport layers. An entirely new approach to the synthesis of monomers for PPV precursors is described in which the 2- and 5- substituents are introduced by directed metallation groups (DMGs) which ultimately become the bis(halomethyl) groups.
Peace RJ, Horton MJ, Péron GLN, et al., 2001, Ligand effects in organoaluminum catalysts for the tacticity control in the synthesis of isotactic poly(methyl methacrylate) [3], Macromolecules, Vol: 34, Pages: 8409-8411, ISSN: 0024-9297
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- Citations: 11
Ridley SH, Ktistakis N, Davidson K, et al., 2001, FENS-1 and DFCP1 are FYVE domain-containing proteins with distinct functions in the endosomal and Golgi compartments., J Cell Sci, Vol: 114, Pages: 3991-4000, ISSN: 0021-9533
FENS-1 and DFCP1 are recently discovered proteins containing one or two FYVE-domains respectively. We show that the FYVE domains in these proteins can bind PtdIns3P in vitro with high specificity over other phosphoinositides. Exogenously expressed FENS-1 localises to early endosomes: this localisation requires an intact FYVE domain and is sensitive to wortmannin inhibition. The isolated FYVE domain of FENS-1 also localises to endosomes. These results are consistent with current models of FYVE-domain function in this cellular compartment. By contrast, exogenously expressed DFCP1 displays a predominantly Golgi, endoplasmic reticulum (ER) and vesicular distribution with little or no overlap with FENS-1 or other endosomal markers. Overexpression of DFCP1 was found to cause dispersal of the Golgi compartment defined by giantin and gpp130-staining. Disruption of the FYVE domains of DFCP1 causes a shift to more condensed and compact Golgi structures and overexpression of this mutant was found to confer significant protection to the Golgi against brefeldin-induced dispersal. These properties of DFCP1 are surprising, and suggest FYVE domain-localisation and function may not be exclusively endosomal. Movies available on-line
Kima TH, Holmes AB, 2001, Synthesis of a conformationally rigid scyllo-inositol polymer as a novel chelating ligand, Journal of the Chemical Society. Perkin Transactions 1, Pages: 2524-2525, ISSN: 1472-7781
A poly(pentyl methacrylate) carrying a conformationally rigid scyllo-inositol substituent (with all axial hydroxy groups) in the 5-position of the pentyl ester chain has been synthesised.
Riehn R, Morgado J, Iqbal R, et al., 2001, Fluorine-substituted poly(p-phenylenes vinylenes) copolymers, Pages: 67-69, ISSN: 0379-6779
We report the electrochemical, optical, and electroluminescent properties of fluorine containing poly(phenylene vinylene) random copolymers. We used 2,3,5,6-tetrafluoro-1,4-phenylene vinylene and 2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene moieties, with ratios of the two copolymer units varying between 5:95 and 27:75. The electron withdrawing effect of fluorine on the conjugated π-electron system was confirmed by electrochemical measurements, which showed an increase of the oxidation and a decrease of the reduction potentials, upon increase of the fluorine content. Light emitting diodes fabricated from the copolymers showed emission in the red-orange, with lower turn-on voltages and higher electroluminescence efficiencies for lower fluorine contents. We observed maximum photoluminescence efficiencies of 6.7%. © 2001 Elsevier Science B.V. All rights reserved.
Early TR, Gordon RS, Carroll MA, et al., 2001, Palladium-catalysed cross-coupling reactions in supercritical carbon dioxide., Chem Commun (Camb), Pages: 1966-1967, ISSN: 1359-7345
Heck and Suzuki reactions proceed in good yield in supercritical carbon dioxide in the presence of palladium acetate and tri-tert-butylphosphine with both free and polymer-tethered substrates.
Ellson CD, Gobert-Gosse S, Anderson KE, et al., 2001, PtdIns(3)P regulates the neutrophil oxidase complex by binding to the PX domain of p40(phox)., Nat Cell Biol, Vol: 3, Pages: 679-682, ISSN: 1465-7392
The production of reactive oxygen species (ROS) by neutrophils has a vital role in defence against a range of infectious agents, and is driven by the assembly of a multi-protein complex containing a minimal core of five proteins: the two membrane-bound subunits of cytochrome b(558) (gp91(phox) and p22(phox)) and three soluble factors (GTP-Rac, p47(phox) and p67(phox) (refs 1, 2). This minimal complex can reconstitute ROS formation in vitro in the presence of non-physiological amphiphiles such as SDS. p40(phox) has subsequently been discovered as a binding partner for p67(phox) (ref. 3), but its role in ROS formation is unclear. Phosphoinositide-3-OH kinases (PI(3)Ks) have been implicated in the intracellular signalling pathways coordinating ROS formation but through an unknown mechanism. We show that the addition of p40(phox) to the minimal core complex allows a lipid product of PI(3)Ks, phosphatidylinositol 3-phosphate (PtdIns(3)P), to stimulate specifically the formation of ROS. This effect was mediated by binding of PtdIns(3)P to the PX domain of p40(phox). These results offer new insights into the roles for PI(3)Ks and p40(phox) in ROS formation and define a cellular ligand for the orphan PX domain.
Osterod F, Peters L, Kraft A, et al., 2001, Luminescent supramolecular assemblies based on hydrogen-bonded complexes of stilbenecarboxylic acids and dithieno[3,2-b:2′,3′-d]thiophene-2-carboxylic acids with a tris(imidazoline) base, Journal of Materials Chemistry, Vol: 11, Pages: 1625-1633, ISSN: 0959-9428
The synthesis of a number of stilbenecarboxylic acids, tetrazolylstilbenes and dithieno[3,2-b:2′,3′-d]thiophene-2-carboxylic acids is reported. These organic acids form non-covalent complexes with an imidazoline base, 1,3,5-tris(4,5-dihydroimidazol-2-yl)benzene 13. Two X-ray crystal structures confirm hydrogen bonds between carboxylate ligands and meta-positioned protonated imidazoline groups. The complexes possess a surprisingly flat disk-like shape with various close contacts between adjacent molecules. Most stilbene and dithieno[3,2-b:2′,3′-d]thiophene derivatives show strong blue or blue-green photoluminescence in solution, whereas fluorescence in the solid state is almost completely quenched.
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