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New hyperbranched polyarylenes of high molecular weights are synthesized in high yields by copolycyclotrimerizations of diynes 1,4-diethynylbenzene, 4,4′-diethynylbiphenyl, 2,7-diethynylfluorene and 2,5-diethynylthiophene with monoynes 1-heptyne, 1-octyne and 1-dodecyne catalyzed by TaCl5-Ph4Sn in toluene. All the polymers show good solubility in common organic solvents, possess excellent thermal stability, and emit strong deep-blue lights of ∼400 nm with quantum efficiencies up to 98%. The polyarylenes effectively limit 532 nm lasers light, some of which show optical limiting performances superior to that of C60, a well-known optical limiter. 相似文献
2.
Natalia Semagina Eric Joannet Sandra Parra Esther Sulman Albert Renken Lioubov Kiwi-Minsker 《Applied Catalysis A: General》2005,280(2):141-147
Pd nanoparticles (2 nm) stabilized in the micelle core of poly(ethylene oxide)-block-poly-2-vinylpyridine were studied in 2-butyne-1,4-diol partial hydrogenation. Both unsupported micelles (0.6 kgPd/m3) and supported ones on γ-Al2O3 (0.042 wt.% Pd) showed nearly 100% selectivity to 2-butene-1,4-diol up to 94% conversion. The only side product observed was 2-butane-1,4-diol. The catalysis was ascribed to Pd nanoparticles’ surface modified by pyridine units of micelles and alkali reaction medium (pH of 13.4). TOFs over the unsupported and supported catalysts were found to be 0.56 and 0.91 s−1 (at 323 K, 0.6 MPa H2 pressure, solvent 2-propanol/water = 7:3), respectively. Reaction kinetics fit the Langmuir–Hinshelwood model assuming weak hydrogen adsorption. The experiments on the catalyst reuse showed that Pd nanoparticles remain inside the micelle core, but the micelles slightly desorbed (less then 5%) during the catalytic run. 相似文献
3.
A mesoporous silica SBA-15-supported palladium with spindle-like nitrogen donor groups, 1,4-diaza-bicyclo[2.2.2]octane, has been successfully prepared and applied for homocoupling of terminal alkynes. The catalyst exhibited very high activity for terminal alkynes carrying various substitution groups, yields ranging from 70% to 94%, with a significant advantage that air acted as the oxidant. It also showed good reusability, could be easily recovered through filtration and washing, and reused at least five times with virtually no evident loss of catalytic performance. Furthermore, it was also proved to be an effective and air-stable heterogeneous catalyst for Suzuki coupling of aryl halides (X = I, Br) with arylboronic acids. The catalyst was systematically characterized by elemental analysis, X-ray photoelectron spectroscopy, high-resolution transmission electron microscope, nitrogen physical adsorption, Brunauer-Emmett-Teller method and X-ray powder diffraction. The analyses indicated that the mesoporous structure of the materials was retained during the immobilization process. 相似文献
4.
Total Synthesis and Structural Elucidation of Two Unusual Non-Methylene-Interrupted Fatty Acids in Ovaries of the Limpet <Emphasis Type="Italic">Cellana toreuma</Emphasis> 下载免费PDF全文
In our previous study, unusual odd‐numbered dienoic acids with a terminal olefin were found as minor components in ovaries of the Japanese limpet Cellana toreuma, and the synthetic interests have been focused onto their structural confirmation and the inspection into their potential biological activity. Here, we describe an efficient and stereoselective total synthesis of two new unusual dienoic acids, 19:2?7,18 and 21:2?7,20, through a common pathway involving the strategic combination of alkyne‐zipper reaction and Lindlar hydrogenation for the construction of their unique carbon chains. In our synthetic study, 2‐propyn‐1‐ol was at first subjected to alkylation and alkyne‐zipper reaction to form the two fragments, and the subsequent carbon chain elongation was achieved by the usual coupling reaction to obtain the C‐19 and C‐21 products bearing an internal acetylenic group. Then, the internal acetylenic group of these products was subjected to Lindlar hydrogenation to form a Z‐alkenyl moiety, and the subsequent deprotection of the products was carried out under an acidic condition without isomerization of the internal Z‐alkenyl group. Total synthesis of target fatty acids, 19:2?7,18 and 21:2?7,20, was finally accomplished by two‐step oxidation of the resulting alcohols into carboxylic acids in a highly chemoselective manner, and the structures of these unusual natural fatty acids were finally elucidated by identifying the GC–MS spectra of the methyl esters of authentic and synthetic fatty acids. 相似文献
5.
Wai-Yeung Wong Suk-Yue Poon Jian-Xin Shi Kok-Wai Cheah 《Journal of Inorganic and Organometallic Polymers and Materials》2007,17(1):189-200
A series of light-emitting group 14 element-containing organometallic platinum polyynes of the form trans-[–Pt(PBu3)2C≡ CArC≡ C(ER2)C≡ CArC≡ C–]
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(Ar = 9-butylcarbazole-3,6-diyl, ER2 = SiMe2, SiPh2, GeMe2, GePh2) were synthesized and spectroscopically characterized. The solution properties and regiochemical structures of this new structural
class of organosilicon- and organogermanium-based metallopolyynes were studied by IR and NMR (1H, 13C, 29Si, and 31P) spectroscopies. The optical absorption and photoluminescence spectra of these metallopolymers were examined and compared
with their well-defined dinuclear model complexes trans-[Pt(Ph)(PEt3)2C≡ CArC≡ C(ER2)C≡ CArC≡ CPt(Ph)(PEt3)2]. The influence of the heavy platinum atom and the group 14 silyl or germyl structural unit possessing different side group
substituents on the thermal and phosphorescence properties were investigated in detail. We have also established the goal
for studying the evolution of the lowest singlet and triplet excited states with the nature of ER2 unit in these metallopolymers. The present work indicates that the phosphorescence emission efficiency harnessed through
the heavy-atom effect of platinum in the main chain changes significantly with the identity of ER2 in the general orders GeR2 > SiR2 (R = Me, Ph) and EMe2 > EPh2 (E = Si, Ge).
Dedicated to Professor Ian Manners in recognition of his outstanding contribution to inorganic and organometallic polymers. 相似文献
6.
Wai-Yeung Wong Suk-Yue Poon 《Journal of Inorganic and Organometallic Polymers and Materials》2008,18(1):155-162
A novel approach based on conjugation interruption was developed for a luminescent and thermally stable platinum(II) polyyne
polymer trans-[–Pt(PBu3)2C≡C(C6H4)CH2(C6H4)C≡C–]
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(1) containing the diphenylmethane chromophoric spacer. Particular attention was focused on the photophysical properties of
this group 10 polymetallayne and comparison was made to its binuclear model complex trans-[Pt(Ph)(PEt3)2C≡C(C6H4)CH2(C6H4)C≡CPt(Ph)(PEt3)2] (2) and their closest group 11 gold(I) and group 12 mercury(II) neighbors, [MC≡C(C6H4)CH2(C6H4)C≡CM] (M = Au(PPh3) (3), HgMe (4)). The regiochemical structures of these angular-shaped compounds were studied by various spectroscopic analyses. Upon photoexcitation,
each of them emits an intense purple-blue fluorescence emission in the near UV region in dilute fluid solutions at room temperature.
Harvesting of organic triplet emissions harnessed through the strong heavy-atom effects of group 10–12 transition metals was
examined. These metal-containing phenyleneethynylenes spaced by the conjugation-breaking CH2 unit were found to have high optical gaps and high-energy triplet states. The influence of metal and sp3-hybridized methylene conjugation-interrupters on the intersystem crossing rate and the spatial extent of the lowest singlet
and triplet excitons was fully elucidated. Our investigations indicate that high-energy triplet states in these materials
intrinsically give rise to very efficient phosphorescence with fast radiative decays.
Dedicated to Professor Didier Astruc in recognition of his outstanding contribution to metallodendrimers and polymers. 相似文献
7.
Johan Samuelsson Mats Johansson 《Journal of the American Oil Chemists' Society》2001,78(12):1191-1196
Described are the physical and chemical properties of the methyl esters of two uncommon fatty acids: vernolic acid, containing
an epoxy group, and crepenynic acid, containing a triple bond. The incorporation of an epoxy or alkyne group into the fatty
acid structure is shown to greatly affect the properties compared to conventional unsaturated fatty acids. The methyl esters
have been characterized and compared with ordinary fatty acid methyl esters (i.e., methyl oleate and linoleate) with respect
to spectroscopic characterization [1H nuclear magnetic resonance (NMR)], 13C NMR, and Fourier transform infrared), rheological properties, and oxidative reactivity (using chemiluminescence). Both methyl
vernoleate and methyl crepenynate could successfully be produced by transesterification under basic conditions without reaction
of the epoxy or alkyne groups. Rheological measurements showed that the methyl esters had a significantly lower viscosity
compared to their triglyceride analogs. Smaller differences were seen when comparing the different methyl esters where methyl
vernoleate had the highest viscosity due to the presence of the more polar oxirane group. Very large differences were found
with respect to the oxidation rate of the different methyl esters. Methyl crepenynate was shown to oxidize extremely rapidly,
whereas methyl vernoleate was very stable toward oxidation. 相似文献
8.
Wai-Yeung Wong Yanhe Guo Cheuk-Lam Ho 《Journal of Inorganic and Organometallic Polymers and Materials》2009,19(1):46-54
A new series of luminescent group 10–12 metal alkynyl complexes and polyyne polymer containing a central tris(p-ethynylphenyl)amine bridging chromophore were prepared. The regiochemical structures of these triangular-shaped trinuclear
compounds and polymer were studied by various spectroscopic and photophysical analyses. Upon photoexcitation, each of them
emits an intense purple-blue fluorescence emission in the near UV region in dilute fluid solutions at room temperature. Harvesting
of organic triplet emissions observed in the low-energy region harnessed through the strong heavy-atom effects of group 10–12
transition metals was examined and the results were compared among these three neighboring late transition metal elements.
The influence of group 15 nitrogen-based heteroatom on the intersystem crossing rate and the spatial extent of the lowest
singlet and triplet excitons was fully elucidated and a comparison was made to the nearest group 14 and 16 neighbors in the
same row of the Periodic Table.
Dedicated to Professor Takakazu Yamamoto in recognition of his outstanding contribution to the area of transition metal-based
coordination polymers. 相似文献
9.
Hiromi Yamashita Shinichi Kawasaki Yuichi Ichihashi Masato Takeuchi Masaru Harada Masakazu Anpo Catherine Louis Michel Che 《Korean Journal of Chemical Engineering》1998,15(5):491-495
Titanium-silicon (Ti/Si) binary oxides having different Ti content were prepared by the sol-gel method and utilized as photocatalysts
for the hydrogenation and hydrogenolysis of CH2CCH with H2O. The photocatalytic reactivity and selectivity of these catalysts were investigated as a function of the Ti content and
it was found that the hydrogenolysis reaction (C2H6 formation) was predominant in regions of low Ti content, while the hydrogenation reaction (C3H6 formation) proceeded in regions of high Ti content. The in situ photoluminescence, diffuse reflectance absorption, FT-IR,
XAFS (XANES and EXAFS), and XPS spectroscopic investigations of these Ti/Si binary oxides indicated that the titanium oxide
species are highly dispersed in the SiO2 matrices and exist in a tetrahedral coordination exhibiting a characteristic photoluminescence spectrum. The charge transfer
excited state of the tetrahedrally coordinated titanium oxide species plays a significant role in the efficient photoreaction
with a high selectivity for the hydrogenolysis of CH3CCH to produces mainly C2H6 and CH4, while the catalysts involving the aggregated octahedrally coordinated titanium oxide species show a high selectivity for
the hydrogenation of CH3CCH to produce C3H6, being similar to reactions of the powdered TiO2 catalysts. The good parallel relationship between the yield of the photoluminescence and the specific photocatalytic reactivity
of the Ti/Si binary oxides as a function of the Ti content clearly indicates that the high photocatalytic reactivity of the
Ti/Si binary oxides having low Ti content is associated with the high reactivity of the charge transfer excited state of the
isolated titanium oxide species in tetrahedral coordination, [Ti3+-O−]*. 相似文献
10.
Johan?Samuelsson Mats?JohanssonEmail author 《Journal of the American Oil Chemists' Society》2003,80(5):491-496
The oxidation of well-defined FA derivatives has been studied with real-time IR (RTIR) and chemiluminescence (CL) techniques.
Both methyl esters and model oils based on different FA have been studied to reveal the effect of functionality. The FA used
were linoleic and crepenynic acid, the latter with an alkyne functionality. The purpose was to reveal how structural differences
affect the oxidation and how this is monitored with CL and RTIR. Both model oils had longer oxidation induction times than
the corresponding methyl esters, as seen by both IR and CL. Generally, the induction times measured with IR were shorter than
those determined by CL, but the rate of oxidation did not seem to differ much between the model oils and the corresponding
methyl esters. The results also imply that the higher functionality of the model oils gives a greater possibility of intramolecular
addition reactions instead of chain scission during oxidation, making the model oils emit fewer low-M.W. volatiles than the
methyl esters. There is also a difference between methyl crepenynate and methyl linoleate, in that the alkyne functionality
seems to enhance the possibility of chain scission instead of addition reactions. The results presented imply that the CL
signal can be used to monitor the oxidation and the formation of volatile compounds from a FA structure. By combining the
CL measurements with RTIR data, information about the oxidation reactions can be obtained, giving a greater understanding
of what reactions are occurring during oxidation and how they are related to each other. 相似文献
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