Showing papers in "Chemistry Letters in 1999"
TL;DR: Bi2W2O9, Bi2WO6, and Bi3TiNbO9 consisting of layered structure with perovskite slabs interleaved with Bi2O2 layers showed photocatalytic activities for H2 evolution from an aqueous methanol solution and O 2 evolution from aqueously silver nitrate solution.
Abstract: Bi2W2O9, Bi2WO6, and Bi3TiNbO9 consisting of layered structure with perovskite slabs interleaved with Bi2O2 layers showed photocatalytic activities for H2 evolution from an aqueous methanol solution and O2 evolution from an aqueous silver nitrate solution. Bi2WO6 with the Aurivillius structure and a 2.8 eV band gap was active for the O2 evolution reaction under visible light irradiation (λ > 420 nm).
442 citations
TL;DR: In this paper, a bis(salicylaldiminato) titanium complex was synthesized and investigated as ethylene polymerization catalysts, which exhibited one of the highest activities displayed by group 4 transition metal complexes having no cyclopentadienyl ligand(s).
Abstract: New bis(salicylaldiminato) titanium complexes were synthesized and investigated as ethylene polymerization catalysts. These complexes, when activated with methylalumoxane, exhibited one of the highest activities displayed by group 4 transition metal complexes having no cyclopentadienyl ligand(s).
160 citations
TL;DR: The introduction of isopropyl substituents to 2 and 2′ positions of benzothiophene rings of bis(1-benzothiophen-3-yl)hexa-fluorocyclopentene increased the population of anti-parallel conformation and enhanced the quantum yield of the cyclization reaction as discussed by the authors.
Abstract: Introduction of isopropyl substituents to 2 and 2′ positions of benzothiophene rings of bis(1-benzothiophen-3-yl)hexa-fluorocyclopentene increased the population of anti-parallel conformation, and enhanced the quantum yield of the cyclization reaction.
142 citations
TL;DR: Substituted pyrroles are synthesized from γ,δ-unsaturated ketone O-pentafluorobenzoyloximes by the intramolecular Heck-type amination of the olefinic moiety catalyzed by Pd(PPh3)4.
Abstract: Substituted pyrroles are synthesized from γ,δ-unsaturated ketone O-pentafluorobenzoyloximes by the intramolecular Heck-type amination of the olefinic moiety catalyzed by Pd(PPh3)4
119 citations
TL;DR: An artificial lipid bearing a triethoxysilyl head and a dialkyl tail has been synthesized in order to prepare a novel type of organic-inorganic hybrid, "Cerasome" which can form siloxane network on its vesicular surface.
Abstract: An artificial lipid bearing a triethoxysilyl head and a dialkyl tail has been synthesized in order to prepare a novel type of organic-inorganic hybrid, “Cerasome”, which can form siloxane network on its vesicular surface. The Cerasomes were obtained upon vortex mixing of aqueous dispersion of the lipid followed by acid hydrolysis of the head moiety.
115 citations
TL;DR: In this article, a bis(salicylaldiminato) zirconium complex was synthesized and its structure determined by X-ray analysis, which displayed an exceptionally high ethylene polymerization activity of 519 kg-PE/mmol-Zr·h using methylaluminoxane (MAO) as a cocatalyst.
Abstract: A new bis(salicylaldiminato) zirconium complex was synthesized and its structure determined by X-ray analysis. This complex displayed an exceptionally high ethylene polymerization activity of 519 kg-PE/mmol-Zr·h using methylaluminoxane (MAO) as a cocatalyst. In contrast, by using Ph3C+B−(C6F5)4 / iBu3Al as a cocatalyst, the complex furnished polyethylene of exceptionally high molecular weight (Mv; 505 × 104).
112 citations
TL;DR: Hexarhenium(III) clusters [Re6(μ3-E)8(CN)6]4− are luminescent at room temperature with the emission quantum yield and lifetime in the order E2− = Se2− > S2− >> Te2− both in acetonitrile and water.
Abstract: Hexarhenium(III) clusters [Re6(μ3-E)8(CN)6]4− (E2− = S2−, Se2−, Te2−) are luminescent at room temperature with the emission quantum yield and lifetime in the order E2− = Se2− > S2− >> Te2− both in acetonitrile and water.
100 citations
TL;DR: In this article, poly(ethylene oxide) derivatives having both vinyl group and imidazolium salt structure on their ends were prepared and polymerized, and the molten salt domain was provided by changing chloride.
Abstract: Poly(ethylene oxide) (PEO) derivatives having both vinyl group and imidazolium salt structure on their ends were prepared and polymerized. When molten salt domain was provided by changing chloride ...
94 citations
TL;DR: In this paper, Orthorhombic (orth.) SrTa2O6 powder which was hardly obtained by a solid state reaction was easily synthesized by using a strontium borate flux.
Abstract: Orthorhombic (orth.) SrTa2O6 powder which was hardly obtained by a solid state reaction was easily synthesized by using a strontium borate flux. The native SrTa2O6 powder showed photoluminescence and a photocatalytic activity for decomposition of pure water into H2 and O2. The photocatalytic activity was drastically increased by loading a NiO co-catalyst even without pretreatment. The optimum amount of NiO loaded was 0.10 wt%. The quantum yield of the NiO(0.10 wt%)/SrTa2O6 photocatalyst was 7% at least.
86 citations
TL;DR: Fullerene-linked quarter-, octi-, and duodeci-thiophenes have been synthesized and their emission spectra demonstrate efficient intramolecular energy transfer from the thiophene moiety to the fullerene.
Abstract: [60]Fullerene-linked quarter-, octi-, and duodeci-thiophenes have been synthesized, and their emission spectra demonstrate efficient intramolecular energy transfer from the thiophene moiety to the fullerene, whose rate constant largely depends on the chain length of the oligothiophene moiety.
86 citations
TL;DR: In this paper, a conducting polymer with photochromic diarylethene units in the main chain was synthesized, and reversible photochromism was observed in solid film, and photoluminescence and electrical conductivity was observed.
Abstract: A conducting polymer having photochromic diarylethene units in the main chain was synthesized. Reversible photochromism was observed in solid film, and photoluminescence and electrical conductivity...
TL;DR: In this paper, a novel fibrous silica with a gnarled surface structure and an inner tube with bundle-replicated stripes was prepared by sol-gel polymerization of tetraethoxysilane using collagen fibers as a template.
Abstract: A novel fibrous silica with a gnarled surface structure and an inner tube with bundle-replicated stripes was prepared by sol-gel polymerization of tetraethoxysilane using collagen fibers as a template.
TL;DR: A porphyrin henicosamer was designed, synthesized, and structurally characterized using scanning tunnelling microscopy as mentioned in this paper, which was used to synthesize a PPHN.
Abstract: A porphyrin henicosamer was designed, synthesized, and structurally characterized using scanning tunnelling microscopy.
TL;DR: Various rotaxanes were readily synthesized in excellent yields by this method and afforded corresponding rotaxane in 90% yield.
Abstract: A pseudorotaxane was prepared from dibenzo-24-crown-8 and a dibenzylammonium salt possessing dimethylphenyl and hydroxy groups at the both termini. Acylation of the pseudorotaxane by 3,5-dimethylbenzoic anhydride in the presence of tributylphosphine afforded corresponding rotaxane in 90% yield. Various rotaxanes were readily synthesized in excellent yields by this method.
TL;DR: In this paper, a diarylethene having 2-cyanopyrrole rings turned blue upon UV irradiation in ethyl acetate, and was unstable and returned to the colorless open-ring form with a half-life time of 37 s at room temperature.
Abstract: A diarylethene having 2-cyanopyrrole rings turned blue upon UV irradiation in ethyl acetate. The colored form was unstable and returned to the colorless open-ring form with a half-life time of 37 s at room temperature. The activation energy of the thermal fading was obtained to be 32.5 kJ / mol, which is less than half of that of spironaphthoxazine.
TL;DR: The first asymmetric Fujiwara-Moritani reaction catalyzed by chiral Pd(II) complexes was reported in this paper, which represented a catalytic aromatic C-H bond activation-asymmetric olefin coupling reaction.
Abstract: The first example of the asymmetric Fujiwara-Moritani reaction catalyzed by chiral Pd(II) complexes is reported to represent a catalytic aromatic C-H bond activation-asymmetric olefin coupling reaction.
TL;DR: 1-Naphthols efficiently couple with internal alkynes in the presence of an iridium catalyst to selectively afford the corresponding 8-substituted 1-naphthol derivatives.
Abstract: 1-Naphthols efficiently couple with internal alkynes in the presence of an iridium catalyst to selectively afford the corresponding 8-substituted 1-naphthol derivatives
TL;DR: In this article, the reaction of aromatic nitriles with triethoxyvinylsilane is described in the presence of a Ru(H)2(CO)(PPh3)3-catalyst to give the corresponding C-H/olefin coupling products.
Abstract: The reaction of aromatic nitriles with triethoxyvinylsilane proceeded in the presence of a Ru(H)2(CO)(PPh3)3-catalyst to give the corresponding C-H/olefin coupling products in high yields. The nitrile group is capable of directing the ruthenium to the ortho C-H bond via π-bonded mode.
TL;DR: In this article, a mesoporous silica with large pore size, SBA-15, was aluminated through the reaction with aluminum chloride, which showed a good control of aluminum content but little influence on the pore structure.
Abstract: The new mesoporous silica with large pore size, SBA-15, was aluminated through the reaction with aluminum chloride. The present alumination method showed a good control of aluminum content but little influence on the pore structure. Aluminum atoms were incorporated into the framework of SBA-15, which resulted in a new kind of mesoporous acid catalyst.
TL;DR: Phenol-formaldehyde polymers and surfactant assembly was structuralized into lamella and disordered mesophases depending on the surfactants/phenol molar ratio at the synthesis as mentioned in this paper.
Abstract: Phenol-formaldehyde polymers and surfactant assembly was structuralized into lamella and disordered mesophases depending on the surfactant/phenol molar ratio at the synthesis.
TL;DR: In this article, a ferrocene-porphyrin-C60 triad was prepared to mimic efficient photosynthetic multistep electron transfer system, and upon irradiation, the triad produced a long-lived charge-separated state with a high quantum yield.
Abstract: A ferrocene-porphyrin-C60 triad was prepared to mimic efficient photosynthetic multistep electron transfer system. Upon irradiation, the triad produced a long-lived charge-separated state with a high quantum yield, compared with the previously reported artificial photosynthetic triads. The lifetime of the charge separated state increased with increasing the solvent polarity. These results indicate that C60 is an excellent building block as an acceptor in light energy conversion systems.
TL;DR: A stable cyclic dialkylgermylene (1) was synthesized by reductive dechlorination of the corresponding dichlorogermane (6) with sodium as discussed by the authors.
Abstract: A stable cyclic dialkylgermylene (1) was synthesized by reductive dechlorination of the corresponding dichlorogermane (6) with sodium. Germylene 1 is monomeric both in solution and in the solid state, as observed by UV-vis spectroscopy and X-ray crystallography.
TL;DR: Hexarhenium clusters, (n-Bu4N)4[Re6(μ3-S)8X6] (X− = Cl−, Br−, I−) show strong red emission both in the solid state and in solution with the lifetime of a few μs at room temperature as discussed by the authors.
Abstract: Hexarhenium clusters, (n-Bu4N)4[Re6(μ3-S)8X6] (X− = Cl−, Br−, I−) show strong red emission both in the solid state and in solution with the lifetime of a few μs at room temperature.
TL;DR: In this article, a nonenzymatic kinetic resolution of racemic secondary alcohols is used to obtain optically active compounds in organic chemistry, using only 0.3 mol% of chiral diamine derived from (S)-proline combined with 0.5 equivalent of triethylamine.
Abstract: Nonenzymatic kinetic resolution of racemic secondary alcohols is an efficient synthetic method to obtain optically active compounds in organic chemistry. Catalytic asymmetric acylation of racemic secondary alcohols has been successfully performed with achiral benzoyl chloride in the presence of only 0.3 mol% of chiral diamine (3) derived from (S)-proline, combined with 0.5 equivalent of triethylamine. This asymmetric acylation of various racemic cyclic secondary alcohols, 5, 6, or 8 membered cycloalkanols (1a–1c), hydroxyesters (1d and 1e), and bromohydrins (1f and 1g) gave the corresponding optically active benzoates (84–97% ee) and unreacted alcohols (79–95% ee). Racemic acyclic secondary alcohols (1h–1j) were also acylated in moderate enantioselectivity.
TL;DR: In this paper, cyclotriveratrylenophanes were synthesized and their inclusion abilities for fullerenes were examined by UV spectroscopy using Rose and Drago method.
Abstract: Cyclotriveratrylenophanes were synthesized and their inclusion abilities for fullerenes were examined by UV spectroscopy. From the spectra, the association constants were determined using Rose and Drago method. Cyclotriveratrylene hosts showed shape-selective properties and large association constants up to 19400 ± 110 dm3mol−1 for C60 and 26500 ± 260 dm3mol−1 for C70
TL;DR: In this article, a multilayered polyaniline was constructed with electrically insulating emeraldine base layers and electrically conducting (±)-10-camphorsulfonic acid (CSA)-doped emeraldines salt layers.
Abstract: Thermoelectric performance of polyaniline can be improved by formation of multilayered film structure. The alternatively layered films are composed of electrically insulating emeraldine base layers and electrically conducting (±)-10-camphorsulfonic acid (CSA)-doped emeraldine salt layers. The multilayered film exhibited 3.5 times higher thermoelectric power factor at ca. 300 K than a bulk film of polyaniline doped by CSA.
TL;DR: In this paper, the Ru3(CO)12-catalyzed reaction of 4,4-dimethyl-2-(2-methylphenyl)-5,6-dihydro-4H-1,3-oxazine with triethoxyvinylsilane gave a mixture of the corresponding 1:1 addition product (3a) and its olefinic analogue (3b) in good yields in ca a 1: 1 ratio.
Abstract: Catalytic C-H/olefin coupling can be directed by N,O-heterocyclic substituents The Ru3(CO)12-catalyzed reaction of 4,4-dimethyl-2-(2-methylphenyl)-5,6-dihydro-4H-1,3-oxazine (1) with triethoxyvinylsilane gave a mixture of the corresponding 1:1 addition product (3a) and its olefinic analogue (3b) in good yields in ca a 1:1 ratio In the case of the reaction of 4,4-dimethyl-2-(2-methylphenyl)-4,5-dihydro-1,3-oxazole (7), the olefinic analogue (8b) of the coupling product (8a) was obtained as the major product The existence of a new reaction pathway is discussed
TL;DR: In this paper, a self-assembled monolayer (SAM) of decanethiol on Au(111) surface was examined by scanning tunneling microscopy (STM) and electrochemical reductive desorption measurement in 0.5 M KOH aqueous solution.
Abstract: Structures of self-assembled monolayer (SAM) of decanethiol on Au(111) surface prepared in ethanol, toluene, DMF and heptane solution were examined by scanning tunneling microscopy (STM) and electrochemical reductive desorption measurement in 0.5 M KOH aqueous solution. While no significant difference was detected in the reductive desorption measurement except for the SAM prepared in heptane, the STM observation showed that domain size and pit size were strongly affected by solvent.
TL;DR: In this article, single-crystal X-ray analysis has shown that p-tert-butylthiacalix[4]arene (H4L) binds to Zn2+ ion by bridging sulfur atoms in addition to phenolic oxygen atoms to form [Zn4L(H2L)2]
Abstract: Single-crystal X-ray analysis has shown that p-tert-butylthiacalix[4]arene (H4L) binds to Zn2+ ion by bridging sulfur atoms in addition to phenolic oxygen atoms to form [Zn4L(H2L)2].
TL;DR: Phenols undergo pentaarylation around the oxygen upon a single treatment with excess aryl bromides in the presence of a palladium catalyst system to produce 2-(1,1′-biphenyl-2-yl)-6-( 1, 1′:3′,1″-terphenyl- 2′-yl)phenol derivatives.
Abstract: Phenols undergo pentaarylation around the oxygen upon a single treatment with excess aryl bromides in the presence of a palladium catalyst system to produce 2-(1,1′-biphenyl-2-yl)-6-(1,1′:3′,1″-terphenyl-2′-yl)phenol derivatives.