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931.
Yu‐Liang Shan Dr. Wai‐Leung Yim Dr. Cheuk‐Wai So 《Angewandte Chemie (International ed. in English)》2014,53(48):13155-13158
The synthesis of an N‐heterocyclic silylene‐stabilized digermanium(0) complex is described. The reaction of the amidinate‐stabilized silicon(II) amide [LSiN(SiMe3)2] ( 1 ; L=PhC(NtBu)2) with GeCl2?dioxane in toluene afforded the SiII–GeII adduct [L{(Me3Si)2N}Si→GeCl2] ( 2 ). Reaction of the adduct with two equivalents of KC8 in toluene at room temperature afforded the N‐heterocyclic carbene silylene‐stabilized digermanium(0) complex [L{(Me3Si)2N}Si→ Ge?Ge←Si{N(SiMe3)2}L] ( 3 ). X‐ray crystallography and theoretical studies show conclusively that the N‐heterocyclic silylenes stabilize the singlet digermanium(0) moiety by a weak synergic donor–acceptor interaction. 相似文献
932.
The Ramanujan Journal - Recently, Andrews, Dixit, and Yee defined two partition functions $$p_{\omega }(n)$$ and $$p_{\nu }(n)$$ that are related with Ramanujan’s mock theta functions... 相似文献
933.
Yi Ren Xi‐Guang Wei Si‐Jia Ren Kai‐Chung Lau Ning‐Bew Wong Wai‐Kee Li 《Journal of computational chemistry》2013,34(23):1997-2005
In order to explore the existence of α‐effect in gas‐phase SN2@N reactions, and to compare its similarity and difference with its counterpart in SN2@C reactions, we have carried out a theoretical study on the reactivity of six α‐oxy‐Nus (FO?, ClO?, BrO?, HOO?, HSO?, H2NO?) in the SN2 reactions toward NR2Cl (R = H, Me) and RCl (R = Me, i‐Pr) using the G2(+)M theory. An enhanced reactivity induced by the α‐atom is found in all examined systems. The magnitude of the α‐effect in the reactions of NR2Cl (R = H, Me) is generally smaller than that in the corresponding SN2 reaction, but their variation trend with the identity of α‐atom is very similar. The origin of the α‐effect of the SN2@N reactions is discussed in terms of activation strain analysis and thermodynamic analysis, indicating that the α‐effect in the SN2@N reactions largely arises from transition state stabilization, and the “hyper‐reactivity” of these α‐Nus is also accompanied by an enhanced thermodynamic stability of products from the n(N) → σ*(O?Y) negative hyperconjugation. Meanwhile, it is found that the reactivity of oxy‐Nus in the SN2 reactions toward NMe2Cl is lower than toward i‐PrCl, which is different from previous experiments, that is, the SN2 reactions of NH2Cl is more facile than MeCl. © 2013 Wiley Periodicals, Inc. 相似文献
934.
Hui‐Xian Yeong Dr. Hong‐Wei Xi Dr. Yongxin Li Dr. Sophy Bhasi Kunnappilly Prof. Dr. Bozhen Chen Prof. Dr. Kai‐Chung Lau Prof. Dr. Hajime Hirao Prof. Dr. Kok Hwa Lim Prof. Dr. Cheuk‐Wai So 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(43):14726-14731
The syntheses of a zwitterionic base‐stabilized digermadistannacyclobutadiene and tetragermacyclobutadiene supported by amidinates and low‐valent germanium amidinate substituents are described. The reaction of the amidinate GeI dimer, [LGe:]2 ( 1 , L=PhC(NtBu)2), with two equivalents of the amidinate tin(II) chloride, [LSnCl] ( 2 ), and KC8 in tetrahydrofuran (THF) at room temperature afforded a mixture of the zwitterionic base‐stabilized digermadistannacyclobutadiene, [L2Ge2Sn2L′2] ( 3 ; L′=LGe:), and the bis(amidinate) tin(II) compound, [L2Sn:] ( 4 ). Compound 3 can also be prepared by the reaction of 1 with [LArSnCl] ( 5 , LAr=tBuC(NAr)2, Ar=2,6‐iPr2C6H3) in THF at room temperature. Moreover, the reaction of 1 with the “onio‐substituent transfer” reagent [4‐NMe2‐C5H4NSiMe3]OTf ( 8 ) in THF and 4‐(N,N‐dimethylamino)pyridine (DMAP) at room temperature afforded a mixture of the zwitterionic base‐stabilized tetragermacyclobutadiene, [L4Ge6] ( 9 ), the amidinium triflate, [PhC(NHtBu)2]OTf ( 10 ), and Me3SiSiMe3 ( 11 ). X‐ray structural data and theoretical studies show conclusively that compounds 3 and 9 have a planar and rhombic charge‐separated structure. They are also nonaromatic. 相似文献
935.
Yunyun Zhou Neil J. Lawrence Dr. Lu Wang Dr. Lingmei Kong Tai‐Sing Wu Dr. Jing Liu Dr. Yi Gao Dr. Joseph R. Brewer Vivianna K. Lawrence Prof. Dr. Renat F. Sabirianov Prof. Dr. Yun‐Liang Soo Prof. Dr. Xiao Cheng Zeng Prof. Dr. Peter A. Dowben Prof. Dr. Wai Ning Mei Prof. Dr. Chin Li Cheung 《Angewandte Chemie (International ed. in English)》2013,52(27):6936-6939
936.
937.
Wai Him Kwok Emmie N. M. Ho Ming Yip Lau Gary N. W. Leung April S. Y. Wong Terence S. M. Wan 《Analytical and bioanalytical chemistry》2013,405(8):2595-2606
In recent years, there has been an ongoing focus for both human and equine doping control laboratories on developing detection methods to control the misuse of peptide therapeutics. Immunoaffinity purification is a common extraction method to isolate peptides from biological matrices and obtain sufficient detectability in subsequent instrumental analysis. However, monoclonal or polyclonal antibodies for immunoaffinity purification may not be commercially available, and even if available, such antibodies are usually very costly. In our study, a simple mixed-mode anion exchange solid-phase extraction cartridge was employed for the extraction of seven target peptides (GHRP-1, GHRP-2, GHRP-6, ipamorelin, hexarelin, CJC-1295, and N-acetylated LKKTETQ (active ingredient of TB-500)) and their in vitro metabolites from horse plasma. The final extract was subject to ultra-high-performance liquid chromatographic separation and analysed with a hybrid high-resolution mass spectrometer. The limits of detection for all seven peptides were estimated to be less than 50 pg/mL. Method validation was performed with respect to specificity, precision, and recovery. The applicability of this multi-analyte method was demonstrated by the detection of N-acetylated LKKTETQ and its metabolite N-acetylated LK from plasma samples obtained after subcutaneous administration of TB-500 (10 mg N-acetylated LKKTETQ) to two thoroughbred geldings. This method could easily be modified to cover more bioactive peptides, such as dermorphin, β-casomorphin, and desmopressin. With the use of high-resolution mass spectrometry, the full-scan data acquired can also be re-processed retrospectively to search for peptides and their metabolites that have not been targeted at the time of analysis. To our knowledge, this is the first identification of in vitro metabolites of all the studied peptides other than TB-500 in horses. Figure
Product-ion scans and mass spectral assignments of the fragment ions of the seven target peptides 相似文献
938.
This paper describes an innovation of dispersive liquid–liquid microextraction enabling multiple‐component analysis of eight high‐priority food contaminants in two chemically distinctive families: Sudan dyes and phthalate plasticizers. To provide convenient sample handling for solid and solid‐containing matrices, a modified dispersive liquid–liquid microextraction procedure used an extractant precoated frit to perform simultaneous filtration, solvent mixing, and phase dispersion in one simple step. A binary ionic liquid extractant system was carefully tuned to deliver high quality analysis based only on affordable LC with diode array detector instrumentation. The method is comprehensively validated for robust quantification with good precision (6.9–9.8% RSD) in a linear 2–1000 μg/L range. Having accomplished enrichment factors up to 451, the treatment enables sensitive detection at 0.09–1.01 μg/L levels. Analysis of six high‐risk solid condiments and sauces further verified its practical applicability within a 70–120% recovery range. Compared to other approaches, the current dispersive liquid–liquid microextraction treatment offers major advantages in terms of minimal solvent (1.5 mL) and sample (0.1 g) consumption, ultra‐high analytical throughput (6 min), and the ability to handle complex solid matrices. The idea of performing simultaneous analysis for multiple contaminants presented here fosters a more effective mode of operation in food control routines. 相似文献
939.
Huaqiong Li Yee Shan Wong Feng Wen Kee Woei Ng Gary Ka Lai Ng Subbu S. Venkatraman Freddy Yin Chiang Boey Lay Poh Tan 《Macromolecular bioscience》2013,13(3):299-310
Direct laser machining and electrospinning are utilized to obtain a bi‐layered hybrid scaffold with hierarchical topographical features to mimic extracellular matrix‐like microenvironment of cells. Adult bone marrow derived human mesenchymal stem cells (hMSCs) are cultured in vitro in these hybrid scaffolds, and cell orientation, proliferation, viability, and differentiation are evaluated. The results show that this novel hybrid scaffold not only supports cell growth like traditional scaffolds, but also elicits positive responses from the cells, like lineage commitment and alignment, which are essential features of future scaffolds.
940.
Yi Yuan Guo‐Qiang Zhang Feng Lu Prof. Qing‐Xiao Tong Qing‐Dan Yang Hin‐Wai Mo Dr. Tsz‐Wai Ng Dr. Ming‐Fai Lo Dr. Zheng‐Qing Guo Chuan Wu Prof. Chun‐Sing Lee 《化学:亚洲杂志》2013,8(6):1253-1258
A new triphenylamine‐bridged fluoranthene derivative, 4‐(7,10‐diphenylfluoranthen‐8‐yl)‐N‐[4‐(7,10‐diphenylfluoranthen‐8‐yl)phenyl]‐N‐phenylaniline (BDPFPA), with a high glass transition temperature of 220 °C has been synthesized and characterized. BDPFPA is a highly fluorescent and versatile material that can be used as a nondoped green emitter and as a hole transporter. BDPFPA was used in a standard trilayer device as the emitting layer, which showed a low turn‐on voltage (<3 V) and a high efficiency of 11.6 cd A?1. The device also shows little efficiency roll‐off at high brightness. For example, the efficiency can still be maintained at 11.4 cd A?1 (5.4 lm W?1) at a brightness of 10 000 cd m?2. These results are among the best reported for nondoped fluorescent green organic light‐emitting diodes. A simple bilayer device, in which BDPFPA serves as a hole‐transporting layer, has a maximum power efficiency of 3.3 lm W?1 and the performance is nearly 40 % higher than that of an N,N′‐bis(1‐naphthyl)‐N,N′‐ diphenyl‐1,1′‐biphenyl‐4,4′‐diamine (NPB)‐based standard device. 相似文献