Showing papers by "Andrew B. Holmes published in 2005"
TL;DR: Suzuki copolymerization of dibromo and bis(boronate) monomers afforded poly(9,9-dihexyl-2,7-dibenzosilole) which showed better efficiency than the corresponding polyfluorene in a single layer light emitting device.
Abstract: 2,7-Disubstituted dibenzosilole monomers have been prepared by the selective trans-lithiation of 4,4'-dibromo-2,2'-diiodobiphenyl followed by silylation with dichlorodihexylsilane. Suzuki copolymerization of dibromo and bis(boronate) monomers afforded poly(9,9-dihexyl-2,7-dibenzosilole) which showed better efficiency than the corresponding polyfluorene in a single layer light emitting device. Preliminary studies demonstrated this to be a promising blue light emitting polymer.
254 citations
TL;DR: In this article, a new class of polyfluorene derivatives modified by insertion of functional groups at the bridging points (position C9), so as to increase inter-ring torsion angles.
Abstract: The color purity of polyfluorene-based blue-emitting polymers is often compromized by “long-wavelength” green emission bands, attributed to polymer interchain species first and more recently to formation of emissive fluorenone defects. Here, we study the nature and the suppression of such bands via characterization of a new class of polyfluorene derivatives modified by insertion of functional groups at the bridging points (position C9), so as to increase inter-ring torsion angles. We find that the solid-state photoluminescence spectra of random copolymers of the modified polyfluorenes and the homopolymer display a progressive decrease of the long-wavelength emission. Electroluminescence spectra also show efficient suppression of such bands in the copolymers with a concentration of ‘twisted' comonomer units of 40 % or greater. Quantum-chemical calculations on model oligomers address the influence of the bridging unit on the torsion angles, and the resulting excited-state properties; the impact on molecular packing is also explored with force-field calculations. We conclude that increase of intra-biphenyl torsion angles is a viable strategy for suppression of long-wavelength emission bands in polyfluorenes.
104 citations
TL;DR: Suzuki cross-coupling reactions are effected in both conventional organic solvents and in batch mode in supercritical carbon dioxide (scCO2) in the presence of palladium(II) acetate microencapsulated in polyurea [PdEnCat] and tetra-n-butylammonium salts.
101 citations
TL;DR: The photo- and electroluminescence properties of a series of novel, heteroleptic, mer-cyclometallated iridium complexes have been fine-tuned from green to blue by changing the substituents on the pyridyl ring of the phenylpyridinyl ligand.
99 citations
TL;DR: Suzuki copolymerisation afforded poly(9,9-dioctyl-3,6-dibenzosilole) which has a sufficiently high triplet energy to function as a host for green electrophosphorescent emitters.
85 citations
TL;DR: Extension of the methodology to the N-arylation of N-silyldiarylamines, N-dicyclohexylphosphino-2',4',6'-triisopropyl-1,1'-biphenyl (X-Phos)(2 mol%) enabled the catalytic amination of aryl bromides and chlorides with N- silylanilines to be realised in excellent yield.
Abstract: Palladium catalysed C–N bond formation in supercritical carbon dioxide has been accomplished. Carbamic acid formation is avoided in part through the use of an N-silylamine as the coupling partner. Employing a catalyst system of Pd2dba3
(1 mol%) and 2-dicyclohexylphosphino-2′,4′,6′-triisopropyl-1,1′-biphenyl (X-Phos)
(2 mol%) enabled the catalytic amination of aryl bromides and chlorides with N-silylanilines to be realised in excellent yield. Extension of the methodology to the N-arylation of N-silyldiarylamines, N-silylazoles and N-silylsulfonamides is reported.
52 citations
TL;DR: Acyl-Pictet-Spengler cyclizations can be achieved in scCO2/CO2-expanded liquid media via the in situ formation of carbamate derivatives of beta-arylethylamines.
29 citations
TL;DR: In this article, the first time for solubility data were obtained for phenylboric acid, iodobenzene, and biphenyl in carbon dioxide at (353 and 383) K and between pressures of (100 to 300) bar.
Abstract: Solubility data were obtained for the first time for phenylboric acid, iodobenzene, and biphenyl in carbon dioxide at (353 and 383) K and between pressures of (100 to 300) bar. Data were obtained u...
22 citations
TL;DR: The enantioselective synthesis of a simplified eleutherobin analogue by ring closing metathesis of the 2,9-divinyl-substituted tetrahydro-oxonin is described; the analogue and an advanced intermediate revealed microtubule stabilising properties in the micromolar range.
19 citations
TL;DR: In this article, the influence of simple shear flow on steady state fluorescence emission from MEH-PPV and two other poly(p-phenylenevinylene) derivatives, in dilute solution and a polystyrene matrix, was investigated.
5 citations
TL;DR: In this article, a blue light emitting poly(9,9-dihexyl-2,7-dibenzosilole) was proposed for multicolor display applications.
Abstract: For multicolor display applications, polymeric light emitters of the three primary colors of red, green and blue are required. Emitters of high luminescence efficiency and long lifetime stability for red and green have been found, but the search for a suitable blue emitter continues. 2,7-Disubstituted dibenzosilole monomers have been prepared by the selective translithiation of 4,4'-dibromo-2,2' diiodobiphenyl followed by silylation with dichlorodihexylsilane. Suzuki copolymerization of dibromo and bis(boronate) monomers afforded poly(9,9-dihexyl-2,7-dibenzosilole) which showed better color stability and efficiency than the corresponding polyfluorene in a single layer light emitting device. Preliminary studies demonstrated this to be a promising blue light emitting polymer.
28 Jan 2005
TL;DR: In this paper, a synthesis of the halogenated medium-ring ether natural product (+)-obtusenyne was reported utilizing a Claisen rearrangement and an intramolecular hydrosilation as key steps.
Abstract: A synthesis of the halogenated medium-ring ether natural product (+)-obtusenyne is reported utilizing a Claisen rearrangement and an intramolecular hydrosilation as key steps.
Patent•
23 Dec 2005
TL;DR: In this article, a composition polymere conductrice comprenant un polymer conducteur dans un polyelectrolyte solide is presented, which concerne une composition polyme conductrice.
Abstract: La presente invention concerne une composition polymere conductrice comprenant un polymere conducteur dans un polyelectrolyte solide.
TL;DR: In this paper, the triplet energy of poly(2,7-dibenzosilole was measured as 2.14 eV, a figure that is slightly higher than that of polyfluorene (2.09 eV) and triscyclometalated iridium complexes with blue-to-green emission properties.
Abstract: Electroluminescence from conjugated polymers can be significantly improved by harnessing the energy of their nonemissive triplet states. Poly(2,7-dibenzosilole) has been prepared and its triplet energy has been measured as 2.14 eV, a figure that is slightly higher than that of polyfluorene (2.09 eV). Two new tris-cyclometalated iridium complexes with blue-to-green emission properties have been prepared and characterized.
TL;DR: In this paper, the enantioselective synthesis of a simplified eleutherobin analogue 7 by ring closing metathesis (RCM) of the 2,9-divinyl-substituted tetrahydro-oxonin 5 is described; the analogue and an advanced intermediate 15 revealed microtubule stabilising properties in the micromolar range.
Abstract: The enantioselective synthesis of a simplified eleutherobin analogue 7 by ring closing metathesis (RCM) of the 2,9-divinyl-substituted tetrahydro-oxonin 5 is described; the analogue 7 and an advanced intermediate 15 revealed microtubule stabilising properties in the micromolar range.