The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yasuhiko Shirota - One of the best experts on this subject based on the ideXlab platform.
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exciplex formation at the organic solid state interface yellow emission in organic light emitting diodes using green fluorescent tris 8 quinolinolato aluminum and hole transporting molecular materials with low ionization potentials
Applied Physics Letters, 1998Co-Authors: Koji Itano, Hiromitsu Ogawa, Yasuhiko ShirotaAbstract:The bilayer organic light-emitting diodes using green-fluorescent tris(8-quinolinolato)aluminum (Alq3) as an emitting material and hole-transport materials with low ionization potentials, 1,3,5-tris(3-methylphenylphenylamino)triphenylamine and 4,4′,4″-tris[bis(4-tert-buthylbiphenyl4-yl)amino]triphenylamine, emitted bright yellow light instead of green light. The yellow emission is attributed to exciplex formation at the solid interface between Alq3 and the hole-transport material. The exciplex formation was evidenced by the measurement of the photoluminescence spectra and lifetimes of the mixture of an equimolar amount of Alq3 and each of the hole-transport materials. The emission color can be tuned by varying the applied voltage.
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multilayered organic electroluminescent device using a novel starburst molecule 4 4 4 tris 3 methylphenylphenylamino triphenylamine as a hole transport material
Applied Physics Letters, 1994Co-Authors: Yasuhiko Shirota, Yoshiyuki Kuwabara, Hiroshi Inada, Takeo Wakimoto, Hitoshi Nakada, Yoshinobu Yonemoto, Shin Kawami, Kunio ImaiAbstract:A novel π‐conjugated starburst molecule, 4,4’,4‘‐tris(3‐methylphenylphenylamino)triphenylamine (m‐MTDATA), which forms a stable amorphous glass, functions as an excellent hole transport material for organic electroluminescent devices. An electroluminescent device consisting of double hole transport layers of m‐MTDATA and 4,4’‐bis(3‐methylphenylphenylamino)biphenyl and an emitting layer of tris(8‐quinolinolato)aluminum exhibits a high luminance efficiency and significant durability.
David Kupfer - One of the best experts on this subject based on the ideXlab platform.
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enantioselective metabolism of the endocrine disruptor pesticide methoxychlor by human cytochromes p450 p450s major differences in selective enantiomer formation by various p450 isoforms
Drug Metabolism and Disposition, 2002Co-Authors: David KupferAbstract:Methoxychlor, a currently used pesticide that in mammals elicits proestrogenic/estrogenic activity and reproductive toxicity, has been classified as a prototype endocrine disruptor. Methoxychlor is prochiral, and its metabolites 1,1,1-trichloro-2-(4-hydroxyphenyl)-2-(4-methoxyphenyl)ethane (mono-OH-M); 1,1,1-trichloro- 2-(4-methoxyphenyl)-2-(3, 4-dihydroxyphenyl)ethane (catechol-M); and 1,1,1-trichloro-2-(4-hydroxyphenyl)-2-(3, 4-dihydroxyphenyl)ethane (tris-OH-M) are chiral; whereas 1,1,1-trichloro-2, 2-bis(4-hydroxyphenyl)ethane (bis-OH-M) is achiral. These metabolites are formed during methoxychlor incubation with liver microsomes or recombinant cytochrome P450s (rP450s). Since methoxychlor-metabolite enantiomers may have different estrogenic/antiestrogenic/antiandrogenic activities than corresponding racemates, the possibility that P450s preferentially generate or use R or S enantiomers, was examined. Indeed, rCYP1A2 and r2A6 mono-demethylated methoxychlor primarily into ( R )-mono-OH-M at 91 and 75%, respectively, whereas rCYP1A1, 2B6, 2C8, 2C9, 2C19, and 2D6 formed the ( S )-enantiomer at 69, 66, 75, 95, 96, and 80%, respectively. However, rCYP3A4, 3A5, and 2B1(rat) weakly demethylated methoxychlor without enantioselectivity. Human liver microsomes generated ( S )-mono-OH-M (77–87%), suggesting that CYP1A2 and 2A6 display only minor catalytic contribution. P450 inhibitors demonstrated that CYP2C9 and possibly 2C19 are major hepatic catalysts forming ( S )-mono-OH-M, and CYP1A2 is primarily involved in forming the ( R )-mono-OH-M. Demethylation rate of ( S )-mono-OH-M versus ( R )-mono-OH-M forming achiral bis-OH-M by rCYP1A2 was 97/3, compared with 15/85 and 17/83 for rCYP2C9 and 2C19, respectively, indicating opposite substrate enantioselectivity of rCYP1A2 versus 2C9 and 2C19. Also, rCYP1A2 preferentially O -demethylated ( R )-catechol-M into ( R )-tris-OH-M (at 80%), contrasting r2C9 and r2C19 that yielded ( S )-tris-OH-M at 80 and 77%, respectively. Ortho -hydroxylation of mono-OH-M into catechol-M and bis-OH-M into tris-OH-M was primarily by 3A4 and was not enantioselective. In conclusion, enantiomeric abundance of methoxychlor metabolites depends on the relative catalytic activity of the hepatic P450 isoforms.
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metabolism of the endocrine disruptor pesticide methoxychlor by human p450s pathways involving a novel catechol metabolite
Drug Metabolism and Disposition, 2002Co-Authors: David KupferAbstract:The metabolism of methoxychlor, a proestrogenic pesticide (endocrine disruptor), was investigated with cDNA expressed human cytochrome P450s and liver microsomes (HLM). In addition to 1,1,1-trichloro-2-(4-hydroxyphenyl)-2-(4-methoxyphenyl)ethane (mono-OH-M), 1,1,1-trichloro-2, 2-bis(4-hydroxyphenyl)ethane (bis-OH-M), and 1,1,1-trichloro-2-(4-hydroxyphenyl)-2-(3, 4-dihydroxyphenyl)ethane (tris-OH-M), a new metabolite was identified as 1,1,1-trichloro-2-(4-methoxyphenyl)-2-(3, 4-dihydroxyphenyl)ethane (catechol-M; previously assumed to be ring-OH-M) and as a key metabolic intermediate. A novel metabolic route was proposed involving methoxychlor O-demethylation to mono-OH-M, followed by bifurcation of the pathway, both leading to the same final product tris-OH-M: pathway a, mono-OH-M is demethylated to bis-OH-M, followed by ortho-hydroxylation forming tris-OH-M and pathway b, mono-OH-M is ortho-hydroxylated forming catechol-M that is O-demethylated forming tris-OH-M. Among the human cDNA-expressed P450s examined, CYP1A2, 2A6, 2C8, 2C9, 2C19, and 2D6 exhibited mainly O-demethylation, with CYP2C19 being the most catalytically competent. CYP3A4, 3A5, and rat 2B1 catalyzed primarily ortho-hydroxylation of mono-OH-M (CYP3A4 being catalytically the most active) but were weak in O-demethylation. CYP1A1, 1B1, 2E1, and 4A11 demonstrated little or no catalytic activity. CYP2B6 appeared unique, catalyzing effectively both O-demethylation and ortho-hydroxylation. Thus, CYP2B6 demethylated methoxychlor to mono-OH-M and ortho-hydroxylated the mono-OH-M forming catechol-M; however, 2B6 did not appreciably demethylate mono-OH-M or ortho-hydroxylate bis-OH-M, suggesting a narrow substrate specificity. CYP2C19-catalyzed demethylation of methoxychlor, mono-OH-M and catechol-M, demonstrating relatively good substrate affinity (K(m) = 0.23 - 0.41 microM). However, the 3A4 ortho-hydroxylation of mono-OH-M and bis-OH-M exhibited lower affinity, K(m) = 12 and 25 microM, respectively. Thus, a phenolic group seems essential for efficient ortho-hydroxylation, forming catechol-M and tris-OH-M. Inhibition studies with HLM and P450s indicate that CYP2C9 and likely 2C19 are catalysts of methoxychlor-mono-demethylation.
Marc Lecouvey - One of the best experts on this subject based on the ideXlab platform.
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synthesis of 1 hydroxymethylene 1 1 bis phosphonic acids from acid anhydrides preparation of a new cyclic 1 acyloxymethylene 1 1 bis phosphonic acid
European Journal of Organic Chemistry, 2004Co-Authors: Erwann Guenin, Estelle Degache, J Liquier, Marc LecouveyAbstract:In continuing with our work to find new pathways to bis(phosphonate) structures we report on their synthesis from tris(trimethylsilyl) phosphite and acid anhydride. This new synthesis allows a direct access to a 1-hydroxymethylene-1,1-bis(phosphonic acid) functionalised by a carboxylic function on the side chain. Moreover, we describe the formation of an original cyclic bis(phosphonate) obtained from phthalic anhydride. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Raymond Ziessel - One of the best experts on this subject based on the ideXlab platform.
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energy transfer in molecular dyads comprising metalloporphyrin and ruthenium ii tris 2 2 bipyridyl terminals competition between internal conversion and energy transfer in the upper excited singlet state of the porphyrin
Journal of the American Chemical Society, 1999Co-Authors: Anthony Harriman, Muriel Hissler, And Olivier Trompette, Raymond ZiesselAbstract:The photophysical properties of a tripartite supermolecule comprising zinc porphyrin and ruthenium(II) tris(2,2‘-bipyridyl) terminals separated by a trans PtII bis-σ-acetylide fragment bearing tri-n-butylphosphine residues have been recorded in solution. Thus, excitation into the ruthenium(II) tris(2,2‘-bipyridyl) fragment is followed by fast intramolecular energy transfer to the triplet state of the porphyrin with only a minor contribution from competing (spin-forbidden) triplet-to-singlet energy transfer. Deactivation of the first excited singlet state localized on the porphyrin involves singlet-to-triplet energy transfer to populate the triplet state of the ruthenium(II) tris(2,2‘-bipyridyl) complex, which rapidly transfers excitation energy to the triplet state of the porphyrin. There is no experimental evidence in support of intramolecular electron transfer between the terminals, such processes being inhibited by poor thermodynamics and by the barrier imposed by the central PtII bis-σ-acetylide fragm...
Matthias Westerhausen - One of the best experts on this subject based on the ideXlab platform.
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formation of calcium carbon bonds from a lewis acid base reaction of calcium bis bis trimethylsilyl amide and tris trimethylsilylmethyl alane
European Journal of Inorganic Chemistry, 1999Co-Authors: Matthias Westerhausen, Christin Birg, Heinrich Noth, Jorg Knizek, Thomas SeifertAbstract:Treatment of calcium bis[bis(trimethylsilyl)amide] with two equivalents of tris(trimethylsilylmethyl)alane yields (Me3SiCH2)2Al–N(SiMe3)2 (1) and the dimer [(Me3Si)2N–Ca(μ–CH2SiMe3)2Al(CH2SiMe3)2]2 (2). The five-coordinate bridging carbon atoms show Ca–C bond lengths of 264 and 268 pm. A similar reaction with calcium bis[bis(trimethylsilyl)phosphanide] gives the dimer [(Me3SiCH2)2Al–P(SiMe3)2]2 (3) with crystallographic C2 symmetry. A calcium-containing species is not isolable, however, in the presence of DME – ether cleavage reactions and the formation of the centrosymmetric dimer [(Me3SiCH2)2Al–OCH2CH2OMe]2 (4) are observed. The central moiety is an Al2O2 cycle with fivefold coordinated aluminium centers.
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bis trimethylsilyl amide und methanide des yttriums molekulstrukturen von tris diethylether o lithium μ chloro tris bis trimethylsilyl methyl yttriat solvensfreiem yttrium tris bis trimethylsilyl amid sowie dem bis benzonitril komplex
Zeitschrift für anorganische und allgemeine Chemie, 1995Co-Authors: Matthias Westerhausen, Manfred Hartmann, Arno Pfitzner, W SchwarzAbstract:Die Reaktion von Yttrium(III)-chlorid mit der dreifachen molaren Menge LiE(SiMe3)2 (E = N, CH) ergibt die entsprechenden Yttrium-Derivate. Yttrium-tris[bis(trimethylsilyl)amid] kristallisiert in der Raumgruppe P31c mit a = 1 636,3(2), c = 849,3(2) pm, Z = 2. Das Yttriumatom ist trigonal pyramidal koordiniert mit YN-Bindungslangen von 222 pm. Entlang der c-Achse sind Benzolmolekule eingeschlossen. Die Verbindung mit E = CH kristallisiert als (Et2O)3LiCl-Addukt in der monoklinen Raumgruppe P21/n mit a = 1 111,8(2), b = 1 865,2(6), c = 2598,3(9) pm, β = 97,41(3)° und Z = 4. Die Umsetzung von Yttrium-tris[bis(trimethylsilyl)amid] mit Benzonitril ergibt einen Bis(benzonitril)-Komplex, der in der triklinen Raumgruppe P1 mit a = 1173,7(2), b = 1210,3(2), c = 1912,4(3) pm, α = 94,37(1), β = 103,39(1), γ = 117,24(1)° und Z = 2 kristallisiert. Die Amido-Liganden sind aquatorial, die Benzonitril-Molekule axial koordiniert. Bis(trimethylsilyl)amides and -methanides of Yttrium — Molecular Structures of Tris(diethylether-O)lithium-(μ-chloro)-tris[bis(trimethylsilyl)methyl]yttriate, solvent-free Yttrium Tris[bis(trimethylsilyl)amide] as well as the Bis(benzonitrile) Complex The reaction of yttrium(III) chloride with the three-fold molar amount of LiE(SiMe3)2 (E = N, CH) yields the corresponding yttrium derivatives. Yttrium tris-[bis(trimethylsilyl)amide] crystallizes in the space group P31c with a = 1 636,3(2), c = 849,3(2) pm, Z = 2. The yttrium atom is surrounded trigonal pyramidal by three nitrogen atoms with YN-bond lengths of 222 pm. Benzene molecules are incorporated parallel to the c-axes. The compound with E = CH crystallizes as a (Et2O)3LiCl-adduct in the monoclinic space group P21/n with a = 1 111,8(2), b = 1 865,2(6), c = 2 598,3(9) pm, β = 97,41(3)° and Z = 4. The reaction of yttrium tris[bis(trimethylsilyl)amide] with benzonitrile yields the bis(benzonitrile) complex, which crystallizes in the triclinic space group P1 with a = 1 173,7(2), b = 1 210,3(2), c = 1 912,4(3) pm, α = 94,37(1), β = 103,39(1), γ = 117,24(1)° and Z = 2. The amido ligands are in equatorial, the benzonitrile molecules in axial positions.