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Toshio Masuda - One of the best experts on this subject based on the ideXlab platform.
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Living polymerization of Phenylacetylenes catalyzed by cationic rhodium complexes bearing tetrafluorobenzobarrelene
Polymer Journal, 2011Co-Authors: Masashi Shiotsuki, Fumio Sanda, Naoya Onishi, Toshio MasudaAbstract:Binary catalysts composed of cationic rhodium complexes, [(tfb)Rh(L)_2]X (tfb: tetrafluorobenzobarrelene, L: phosphine ligand, X: counter anion), and ^ i PrNH_2 induced living polymerization of Phenylacetylene and its ring-substituted derivatives. The living nature was confirmed by kinetic plots of the polymerization. Nuclear magnetic resonance studies revealed that ^ i PrNH_2 serves to dissociate the coordinating PPh_3 ligand of [(tfb)Rh(L)_2]X to form an initiating species. Block copolymers were synthesized by the sequential polymerization of different Phenylacetylenes using the present catalyst. Binary catalysts composed of cationic rhodium complexes, [(tfb)Rh(L)_2]X (tfb: tetrafluorobenzobarrelene, L: phosphine ligand, X: counter anion), and ^ i PrNH_2 induced living polymerization of Phenylacetylene and its ring-substituted derivatives. For instance, [(tfb)Rh(PPh_3)_2]BPh_4 in conjunction with ^ i PrNH_2 polymerized Phenylacetylene in a living manner to yield poly(Phenylacetylene) with narrow molecular weight distribution ( M _w/ M _n 1.09) quantitatively. The living nature was confirmed by kinetic plots of the polymerization. Nuclear magnetic resonance studies revealed that ^ i PrNH_2 serves to dissociate the coordinating PPh_3 ligand of [(tfb)Rh(L)_2]X to form an initiating species. Block copolymers were synthesized by the sequential polymerization of different Phenylacetylenes using the present catalyst.
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living polymerization of Phenylacetylenes catalyzed by cationic rhodium complexes bearing tetrafluorobenzobarrelene
Polymer Journal, 2011Co-Authors: Masashi Shiotsuki, Fumio Sanda, Naoya Onishi, Toshio MasudaAbstract:Binary catalysts composed of cationic rhodium complexes, [(tfb)Rh(L)2]X (tfb: tetrafluorobenzobarrelene, L: phosphine ligand, X: counter anion), and iPrNH2 induced living polymerization of Phenylacetylene and its ring-substituted derivatives. The living nature was confirmed by kinetic plots of the polymerization. Nuclear magnetic resonance studies revealed that iPrNH2 serves to dissociate the coordinating PPh3 ligand of [(tfb)Rh(L)2]X to form an initiating species. Block copolymers were synthesized by the sequential polymerization of different Phenylacetylenes using the present catalyst.
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Synthesis and gas permeation properties of para-substituted poly(1-chloro-2-Phenylacetylenes)
Macromolecules, 2006Co-Authors: Yusuke Taniguchi, Toshikazu Sakaguchi, Masashi Shiotsuki, Fumio Sanda, Toshio MasudaAbstract:Para-substituted 1-chloro-2-Phenylacetylenes [ClC≡CC6H4-p-R; R = F (1), Cl (2), Me (3), Br (4), I (5), CF3 (6), SiMe3 (7), SiEt3 (8), Si(n-Pr)3 (9), and Si(i-Pr)3 (10)] were polymerized with a catalyst generated by UV irradiation of Mo(CO)6 in CCl4 to provide the corresponding polymers. The formed polymers except poly(5) were soluble in common organic solvents and afforded free-standing membranes by the casting method except for poly(10) whose molecular weight was rather low. Compared to poly(1-chloro-2-Phenylacetylene) (PCPA), all the polymers in this study exhibited high gas permeability. As the size of para-substituents increased, both the fractional free volume (FFV) and gas permeability increased and then decreased. Consequently, poly(6), which has a relatively bulky CF3 group, showed the largest FFV (0.258) and the highest gas permeability (PO2 = 280 barrers). Poly(9) and poly(10) were more gas-permeable than PCPA despite their small FFV values and showed large diffusion coefficients, which might be...
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Degradation behavior of stereoregular cis-transoidal poly(Phenylacetylene)s
Journal of Polymer Science Part A: Polymer Chemistry, 2001Co-Authors: S. M. Abdul Karim, Ryouji Nomura, Toshio MasudaAbstract:The stability of poly(Phenylacetylene)s in solution was systematically studied. Cis–transoidal poly(Phenylacetylene) prepared with a Rh catalyst readily underwent autoxidative degradation into oligomers, whereas a W-based polymer with a trans-rich geometrical structure degraded slowly under similar conditions. The degradation of W-based poly(Phenylacetylene) was independent of the solvents, whereas the degradation of the cis–transoidal material strongly depended on the solvents, and very rapid degradation was observed in toluene and CHCl3. A reduction in the degradation rate in the absence of oxygen and the appearance of carbonyl groups in an IR spectrum and aldehyde protons in a 1H NMR spectrum of the resulting oligomers indicated the direct participation of oxygen in the degradation where light was supposed to assist the degradation by producing radicals on the main chain. The cis content of cis–transoidal poly(Phenylacetylene) was unchanged during the degradation, unlike for the acid-catalyzed decomposition, in which the cis content decreased linearly as the molecular weight decreased. Ring-substituted poly(Phenylacetylene)s degraded slowly compared with poly(Phenylacetylene), regardless of the kind of substituent, which suggests that steric factors affected the degradation rate. The use of radical scavengers such as 2,2,6,6-tetramethylpiperidine-1-oxyl and diphenylpicrylhydrazil suppressed the decomposition. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3130–3136, 2001
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LIVING METATHESIS POLYMERIZATION OF 1-CHLORO-2-Phenylacetylene BY MoOCI4-BASED CATALYSTS
Journal of Macromolecular Science Part A, 2000Co-Authors: Shigetaka Hayano, Toshio MasudaAbstract:The living polymerization of 1-chloro-2-Phenylacetylene was accomplished by use of the MoOCl4–n–Bu4Sn-EtOH/anisole cata-lyst/solvent system. The polydispersity ratio of the produced poly(1-chloro-2-Phenylacetylene) was as small as 1.1. Living polymerization was verified by the multi-stage polymerization and the monomer-conversion dependence of the molecular weight. Only n-Bu4Sn was effective as cocatalyst of the MoOCl4-based catalyst, and Et3Al, Et2Zn, and n-BuLi were not. Among 1-chloro-2-Phenylacetylene analogues, only para substituted derivatives appeared to polymerize in a living fashion.
Eiji Yashima - One of the best experts on this subject based on the ideXlab platform.
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remarkable enhancement of the enantioselectivity of an organocatalyzed asymmetric henry reaction assisted by helical poly Phenylacetylene s bearing cinchona alkaloid pendants via an amide linkage
ACS Macro Letters, 2012Co-Authors: Zhenglin Tang, Hiroki Iida, Eiji YashimaAbstract:A series of novel helical poly(Phenylacetylene)s bearing amino-functionalized cinchona alkaloid pendant groups connecting to the phenyl rings through an amide linkage were prepared by the polymerization of the corresponding Phenylacetylenes using a rhodium catalyst. All of the polymers formed a preferred-handed helical conformation biased by the optically active pendants, resulting in the induced circular dichroism in their π-conjugated polymer backbone regions. The optically active helical polymers efficiently catalyzed the asymmetric Henry reaction of benzaldehydes with nitromethane, giving optically active products up to 94% enantiomeric excess (ee) when the poly(Phenylacetylene) bearing an amino-functionalized quinine pendant group was used as the polymeric organocatalyst; the enantioselectivity was remarkably higher than those catalyzed by the corresponding nonhelical poly(Phenylacetylene) (18% ee) and the monomer (28% ee).
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amplification of macromolecular helicity of dynamic helical poly Phenylacetylene s bearing non racemic alanine pendants in dilute solution liquid crystal and two dimensional crystal
Polymer Journal, 2012Co-Authors: Sousuke Ohsawa, Katsuhiro Maeda, Shinichiro Sakurai, Kanji Nagai, Jiro Kumaki, Eiji YashimaAbstract:Optically active poly(Phenylacetylene) copolymers composed of non-racemic Phenylacetylenes bearing L- and D-alanine decyl esters as the side groups (poly(1Lm-co-1Dn), m>n) were prepared by the copolymerization of the corresponding L- and D-Phenylacetylenes with different enantiomeric excesses using a rhodium catalyst; their chiral amplification of the helical conformation as an excess of one-handedness in a dilute solution, in a lyotropic liquid-crystalline (LC) state and in a two-dimensional (2D) crystal on substrate was investigated by measuring the circular dichroism spectra of the copolymers at different temperatures, mesoscopic cholesteric twist in the LC state (cholesteric helical pitch) and high-resolution atomic force microscopy images of the self-assembled 2D helix-bundle structures of the copolymer chains, respectively. We have observed a unique amplification of the helical-sense excess (majority rule effect) of dynamic helical, liquid-crystalline (LC) poly(Phenylacetylene)s bearing non-racemic D- and L-alanine residues as the pendant groups in a dilute solution, in the cholesteric LC state and a two-dimensional crystal on substrate. The preferred-handed helical-sense and handedness excess of the copolymers in a dilute solution were sensitive to the solvent polarity and temperature, and amplification of the helical-sense excess was significantly affected by the solvents.
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hierarchical amplification of macromolecular helicity of dynamic helical poly Phenylacetylene s composed of chiral and achiral Phenylacetylenes in dilute solution liquid crystal and two dimensional crystal
Journal of the American Chemical Society, 2011Co-Authors: Sousuke Ohsawa, Katsuhiro Maeda, Shinichiro Sakurai, Kanji Nagai, Jiro Kumaki, Motonori Banno, Eiji YashimaAbstract:Optically active poly(Phenylacetylene) copolymers consisting of optically active and achiral Phenylacetylenes bearing l-alanine decyl esters (1L) and 2-aminoisobutylic acid decyl esters (Aib) as the pendant groups (poly(1Lm-co-Aibn)) with various compositions were synthesized by the copolymerization of the optically active 1L with achiral Aib using a rhodium catalyst, and their chiral amplification of the macromolecular helicity in a dilute solution, a lyotropic liquid crystalline (LC) state, and a two-dimensional (2D) crystal on the substrate was investigated by measuring the circular dichroism of the copolymers, mesoscopic cholesteric twist in the LC state (cholesteric helical pitch), and high-resolution atomic force microscopy (AFM) images of the self-assembled 2D helix-bundles of the copolymer chains. We found that the macromolecular helicity of poly(1Lm-co-Aibn)s could be hierarchically amplified in the order of the dilute solution, LC state, and 2D crystal. In sharp contrast, almost no chiral amplif...
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switching of macromolecular helicity of optically active poly Phenylacetylene s bearing cyclodextrin pendants induced by various external stimuli
Journal of the American Chemical Society, 2006Co-Authors: Katsuhiro Maeda, Hiroaki Mochizuki, And Masaki Watanabe, Eiji YashimaAbstract:A series of novel Phenylacetylenes bearing optically active cyclodextrin (CyD) residues such as α-, β-, and γ-CyD and permethylated β-CyD residues as the pendant groups was synthesized and polymerized with a rhodium catalyst to give highly cis−transoidal poly(Phenylacetylene)s, poly-1α, poly-2β, poly-3γ, and poly-2β-Me, respectively. The polymers exhibited an induced circular dichroism (CD) in the UV−visible region of the polymer backbones, resulting from the prevailing one-handed helical conformations. The Cotton effect signs were inverted in response to external chiral and achiral stimuli, such as temperature, solvent, and interactions with chiral or achiral guest molecules. The inversion of the Cotton effect signs was accompanied by a color change due to a conformational change, such as inversion of the helicity of the polymer backbones with a different twist angle of the conjugated double bonds, that was readily visible with the naked eye and could be quantified by absorption and CD spectroscopies. Th...
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Helical arrays of pendant fullerenes on optically active poly(Phenylacetylene)s.
Chemistry (Weinheim an der Bergstrasse Germany), 2005Co-Authors: Tatsuya Nishimura, Katsuhiro Maeda, Sousuke Ohsawa, Eiji YashimaAbstract:Novel, optically active, stereoregular poly(Phenylacetylene)s bearing the bulky fullerene as the pendant were synthesized by copolymerization of an achiral Phenylacetylene bearing a [60]fullerene unit with optically active Phenylacetylene components in the presence of a rhodium catalyst. The C60-bound Phenylacetylene was prepared by treatment of C60 with N-(4-ethynylbenzyl)glycine in a Prato reaction. The obtained copolymers exhibited induced circular dichroism (ICD) in solution both in the main-chain region and in the achiral fullerene chromophoric region, although their ICD intensities were highly dependent on the structures of the optically active Phenylacetylenes and the solution temperature. These results indicate that the optically active copolymers form one-handed helical structures and that the pendant achiral fullerene groups are arranged in helical arrays with a predominant screw sense along the polymer backbone. The structures and morphology of the copolymers on solid substrates were also investigated by atomic force microscopy.
Katsuhiro Maeda - One of the best experts on this subject based on the ideXlab platform.
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synthesis of stereoregular telechelic poly Phenylacetylene s facile terminal chain end functionalization of poly Phenylacetylene s by terminative coupling with acrylates and acrylamides in rhodium catalyzed living polymerization of Phenylacetylenes
Journal of the American Chemical Society, 2021Co-Authors: Kensuke Echizen, Tatsuya Nishimura, Tsuyoshi Taniguchi, Katsuhiro MaedaAbstract:Various α,β-unsaturated carbonyl compounds, such as acrylates and acrylamides, were quantitatively introduced to the terminal chain end of poly(Phenylacetylene)s by C-C bond formation with terminal organorhodium(I) species formed in the living polymerization of Phenylacetylenes with a rhodium-based multicomponent catalytic system that we have recently developed, when these carbonyl compounds were used as terminating reagents. This enables the facile and versatile synthesis of stereoregular telechelic poly(Phenylacetylene)s with various functional groups at both the initial and terminal chain ends because the components of aryl boronic acid derivatives used as initiators in our multicomponent catalytic system are quantitatively introduced to the initiating end of the resulting polymer.
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Facile and Versatile Synthesis of End‐Functionalized Poly(Phenylacetylene)s: A Multicomponent Catalytic System for Well‐Controlled Living Polymerization of Phenylacetylenes
Angewandte Chemie (International ed. in English), 2020Co-Authors: Tsuyoshi Taniguchi, Tatsuya Nishimura, Kensuke Echizen, Takumi Yoshida, Kokoro Takayama, Katsuhiro MaedaAbstract:A rhodium-based multicomponent catalytic system for well-controlled living polymerization of Phenylacetylenes has been developed. The catalytic system is composed of readily available and bench-stable [Rh(nbd)Cl]2 , aryl boronic acid derivatives, diPhenylacetylene, 50 % aqueous KOH, and PPh3 . This system offers a method for the facile and versatile synthesis of various end-functionalized cis-stereoregular poly(Phenylacetylene)s because components from aryl boronic acids and diPhenylacetylene were introduced to the initiating end of the polymers. The polymerization reaction shows a typical living nature with a high initiation efficiency, and the molecular weight of the resulting poly(Phenylacetylene)s can be readily controlled with very narrow molecular-weight distributions (Mw /Mn =1.02-1.09). The experimental results suggest that the present catalytic system has a higher polymerization activity than the polymerization activities of other rhodium-based catalytic systems previously reported.
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amplification of macromolecular helicity of dynamic helical poly Phenylacetylene s bearing non racemic alanine pendants in dilute solution liquid crystal and two dimensional crystal
Polymer Journal, 2012Co-Authors: Sousuke Ohsawa, Katsuhiro Maeda, Shinichiro Sakurai, Kanji Nagai, Jiro Kumaki, Eiji YashimaAbstract:Optically active poly(Phenylacetylene) copolymers composed of non-racemic Phenylacetylenes bearing L- and D-alanine decyl esters as the side groups (poly(1Lm-co-1Dn), m>n) were prepared by the copolymerization of the corresponding L- and D-Phenylacetylenes with different enantiomeric excesses using a rhodium catalyst; their chiral amplification of the helical conformation as an excess of one-handedness in a dilute solution, in a lyotropic liquid-crystalline (LC) state and in a two-dimensional (2D) crystal on substrate was investigated by measuring the circular dichroism spectra of the copolymers at different temperatures, mesoscopic cholesteric twist in the LC state (cholesteric helical pitch) and high-resolution atomic force microscopy images of the self-assembled 2D helix-bundle structures of the copolymer chains, respectively. We have observed a unique amplification of the helical-sense excess (majority rule effect) of dynamic helical, liquid-crystalline (LC) poly(Phenylacetylene)s bearing non-racemic D- and L-alanine residues as the pendant groups in a dilute solution, in the cholesteric LC state and a two-dimensional crystal on substrate. The preferred-handed helical-sense and handedness excess of the copolymers in a dilute solution were sensitive to the solvent polarity and temperature, and amplification of the helical-sense excess was significantly affected by the solvents.
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hierarchical amplification of macromolecular helicity of dynamic helical poly Phenylacetylene s composed of chiral and achiral Phenylacetylenes in dilute solution liquid crystal and two dimensional crystal
Journal of the American Chemical Society, 2011Co-Authors: Sousuke Ohsawa, Katsuhiro Maeda, Shinichiro Sakurai, Kanji Nagai, Jiro Kumaki, Motonori Banno, Eiji YashimaAbstract:Optically active poly(Phenylacetylene) copolymers consisting of optically active and achiral Phenylacetylenes bearing l-alanine decyl esters (1L) and 2-aminoisobutylic acid decyl esters (Aib) as the pendant groups (poly(1Lm-co-Aibn)) with various compositions were synthesized by the copolymerization of the optically active 1L with achiral Aib using a rhodium catalyst, and their chiral amplification of the macromolecular helicity in a dilute solution, a lyotropic liquid crystalline (LC) state, and a two-dimensional (2D) crystal on the substrate was investigated by measuring the circular dichroism of the copolymers, mesoscopic cholesteric twist in the LC state (cholesteric helical pitch), and high-resolution atomic force microscopy (AFM) images of the self-assembled 2D helix-bundles of the copolymer chains. We found that the macromolecular helicity of poly(1Lm-co-Aibn)s could be hierarchically amplified in the order of the dilute solution, LC state, and 2D crystal. In sharp contrast, almost no chiral amplif...
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switching of macromolecular helicity of optically active poly Phenylacetylene s bearing cyclodextrin pendants induced by various external stimuli
Journal of the American Chemical Society, 2006Co-Authors: Katsuhiro Maeda, Hiroaki Mochizuki, And Masaki Watanabe, Eiji YashimaAbstract:A series of novel Phenylacetylenes bearing optically active cyclodextrin (CyD) residues such as α-, β-, and γ-CyD and permethylated β-CyD residues as the pendant groups was synthesized and polymerized with a rhodium catalyst to give highly cis−transoidal poly(Phenylacetylene)s, poly-1α, poly-2β, poly-3γ, and poly-2β-Me, respectively. The polymers exhibited an induced circular dichroism (CD) in the UV−visible region of the polymer backbones, resulting from the prevailing one-handed helical conformations. The Cotton effect signs were inverted in response to external chiral and achiral stimuli, such as temperature, solvent, and interactions with chiral or achiral guest molecules. The inversion of the Cotton effect signs was accompanied by a color change due to a conformational change, such as inversion of the helicity of the polymer backbones with a different twist angle of the conjugated double bonds, that was readily visible with the naked eye and could be quantified by absorption and CD spectroscopies. Th...
Jeremy D. Semrau - One of the best experts on this subject based on the ideXlab platform.
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differential inhibition in vivo of ammonia monooxygenase soluble methane monooxygenase and membrane associated methane monooxygenase by Phenylacetylene
Environmental Microbiology, 2000Co-Authors: Sonny Lontoh, Alan B Hooper, Alan A. Dispirito, Cinder L. Krema, Mark Whittaker, Jeremy D. SemrauAbstract:Phenylacetylene was investigated as a differential inhibitor of ammonia monooxygenase (AMO), soluble methane monooxygenase (sMMO) and membrane-associated or particulate methane monooxygenase (pMMO) in vivo. At Phenylacetylene concentrations > 1 microM, whole-cell AMO activity in Nitrosomonas europaea was completely inhibited. Phenylacetylene concentrations above 100 microM inhibited more than 90% of sMMO activity in Methylococcus capsulatus Bath and Methylosinus trichosporium OB3b. In contrast, activity of pMMO in M. trichosporium OB3b, M. capsulatus Bath, Methylomicrobium album BG8, Methylobacter marinus A45 and Methylomonas strain MN was still measurable at Phenylacetylene concentrations up to 1,000 microM. AMO of Nitrosococcus oceanus has more sequence similarity to pMMO than to AMO of N. europaea. Correspondingly, AMO in N. oceanus was also measurable in the presence of 1,000 microM Phenylacetylene. Measurement of oxygen uptake indicated that Phenylacetylene acted as a specific and mechanistic-based inhibitor of whole-cell sMMO activity; inactivation of sMMO was irreversible, time dependent, first order and required catalytic turnover. Corresponding measurement of oxygen uptake in whole cells of methanotrophs expressing pMMO showed that pMMO activity was inhibited by Phenylacetylene, but only if methane was already being oxidized, and then only at much higher concentrations of Phenylacetylene and at lower rates compared with sMMO. As Phenylacetylene has a high solubility and low volatility, it may prove to be useful for monitoring methanotrophic and nitrifying activity as well as identifying the form of MMO predominantly expressed in situ.
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Differential inhibition in vivo of ammonia monooxygenase, soluble methane monooxygenase and membrane‐associated methane monooxygenase by Phenylacetylene
Environmental microbiology, 2000Co-Authors: Sonny Lontoh, Alan B Hooper, Alan A. Dispirito, Cinder L. Krema, Mark Whittaker, Jeremy D. SemrauAbstract:Phenylacetylene was investigated as a differential inhibitor of ammonia monooxygenase (AMO), soluble methane monooxygenase (sMMO) and membrane-associated or particulate methane monooxygenase (pMMO) in vivo. At Phenylacetylene concentrations > 1 microM, whole-cell AMO activity in Nitrosomonas europaea was completely inhibited. Phenylacetylene concentrations above 100 microM inhibited more than 90% of sMMO activity in Methylococcus capsulatus Bath and Methylosinus trichosporium OB3b. In contrast, activity of pMMO in M. trichosporium OB3b, M. capsulatus Bath, Methylomicrobium album BG8, Methylobacter marinus A45 and Methylomonas strain MN was still measurable at Phenylacetylene concentrations up to 1,000 microM. AMO of Nitrosococcus oceanus has more sequence similarity to pMMO than to AMO of N. europaea. Correspondingly, AMO in N. oceanus was also measurable in the presence of 1,000 microM Phenylacetylene. Measurement of oxygen uptake indicated that Phenylacetylene acted as a specific and mechanistic-based inhibitor of whole-cell sMMO activity; inactivation of sMMO was irreversible, time dependent, first order and required catalytic turnover. Corresponding measurement of oxygen uptake in whole cells of methanotrophs expressing pMMO showed that pMMO activity was inhibited by Phenylacetylene, but only if methane was already being oxidized, and then only at much higher concentrations of Phenylacetylene and at lower rates compared with sMMO. As Phenylacetylene has a high solubility and low volatility, it may prove to be useful for monitoring methanotrophic and nitrifying activity as well as identifying the form of MMO predominantly expressed in situ.
Hideki Shirakawa - One of the best experts on this subject based on the ideXlab platform.
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Novel liquid-crystalline titanocene complexes with catalytic activity for polymerizations of acetylene and Phenylacetylene
Polymer, 1998Co-Authors: G Piao, Kazuo Akagi, Hiromasa Goto, Hideki ShirakawaAbstract:Abstract We have synthesized a series of novel titanocene complexes with liquid-crystalline (LC) groups as coordination ligands, with the ultimate aim of developing LC catalytic species available for anisotropic polymerizations of acetylenes. The titanocene complexes were prepared by introducing LC groups into cyclopentadienyl ligands as substituents, (PCH506Cp)2TiCl2 (1), or coordinating them to a titanium atom as symmetric and asymmetric ligands, Cp2Ti(PCH5060)2 (2) and Cp2Ti(PCH5060)Cl (3) [where Cp = cyclopentadienyl, PCH506 = p-(trans-4-n-pentylcyclohexyl)phenoxyhexyl and PCH5060 = p-(trans-4-n-pentylcyclohexyl)phenoxyhexyloxy]. Polarizing optical microscope observations and differential scanning calorimetry measurements indicated that the titanocene complexes 2 and 3 are the first titanium complexes exhibiting LC behaviour. It is found that the titanocene complexes 1 and 2 can polymerize Phenylacetylenes to give poly(Phenylacetylene)s with the aid of triethylaluminium (Et3Al) as cocatalyst. The molecular weights and degrees of polymerization of the poly(Phenylacetylene)s prepared were comparable or superior to those prepared with titanocene dichloride and tetra-n-butoxytitanium [Ti(O-n-Bu)4] catalysts. The LC titanocene complexes 2 and 3 were also confirmed to have catalytic activities for the polymerization of acetylene. Electron spin resonance spectra of the catalyst systems gave signals of trivalent titanium (Ti3+) with no hyperfine structure, suggesting that the catalytically active species is a mononuclear complex consisting of Ti3+ rather than a binuclear or trinuclear one.
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Liquid crystalline titanocene with catalytic activity for polymerizations of acetylene derivatives
Synthetic Metals, 1997Co-Authors: Kazuo Akagi, Hideo Bannai, G Piao, Hiromasa Goto, Hideki ShirakawaAbstract:Abstract Two kinds of liquid crystalline (LC) titanocenes have been synthesized with an aim to construct a new type of anisotropic polymerization field. The titanocene derivatives were prepared by introducing LC groups into cyclopentadienyl ligands as substituents, (PCH506Cp) 2 TiCl 2 ( 1 ) or coordinating them to titanium atom as ligands, Cp 2 Ti(PCH5060) 2 ( 2 ). Observations of polarizing optical microscope and measurements of DSC indicated that 2 is the first titanium complex exhibiting a thermotropic LC phase. We found that both the titanocene derivatives can polymerize Phenylacetylenes to give poly(Phenylacetylene)s with an aid of triethylaluminium used as a cocatalyst. Molecular weights and polymerization degrees of the polymers were comparable or superior to those by catalysts such as a titanocene dichloride [Cp 2 TiCl 2 ] and a tetra- n -butoxytitanium [Ti(O- n -Bu) 4 ]. The LC titanocene derivative ( 2 ) was also confirmed to have a high catalytic activity for acetylene polymerization. These results should shed light on development of novel anisotropic reaction field available for syntheses of directly aligned conducting polymers.
