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991.
Guang‐Yao Ran Xing‐Xing Yang Jing‐Fei Yue Wei Du Ying‐Chun Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(27):9308-9312
An atom‐economic and highly efficient vinylogous umpolung strategy is developed for deconjugated carbonyl compounds, which generate electron‐deficient π‐allylpalladium complexes with Pd(OAc)2 under ligand‐free conditions. In cooperation with a chiral‐phosphonium‐based phase‐transfer catalyst, the asymmetric direct oxidative allylic alkylations of 3‐substituted oxindoles are furnished under O2 atmosphere. The γ‐ or even remote ?‐regioselective alkylation products, with substantial substituents, are delivered with excellent enantioselectivity, and can be further used to access diverse chiral spirocyclic architectures effectively. The Mukaiyama dienol silyl ether can be utilized similarly, indicating that the current active π‐allylpalladium species results from tautomerization of the PdII‐dienolate intermediate. 相似文献
992.
Jia Zhang Yue Yuan Minling Gao Zheng Han Chengyan Chu Yuguo Li Peter C. M. vanZijl Mingyao Ying Jeff W. M. Bulte Guanshu Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):9976-9980
While carbon dots (C‐dots) have been extensively investigated pertaining to their fluorescent, phosphorescent, electrochemiluminescent, optoelectronic, and catalytic features, their inherent chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) properties are unknown. By virtue of their hydrophilicity and abundant exchangeable protons of hydroxyl, amine, and amide anchored on the surface, we report here that C‐dots can be adapted as effective diamagnetic CEST (diaCEST) MRI contrast agents. As a proof‐of‐concept demonstration, human glioma cells were labeled with liposomes with or without encapsulated C‐dots and implanted in mouse brain. In vivo CEST MRI was able to clearly differentiate labeled cells from non‐labeled cells. The present findings may encourage new applications of C‐dots for in vivo imaging in deep tissues, which is currently not possible using conventional fluorescent (near‐infrared) C‐dots. 相似文献
993.
Hongwei Wu Zhao Chen Weijie Chi Anivind Kaur Bindra Long Gu Cheng Qian Bing Wu Bingbing Yue Guofeng Liu Guangbao Yang Liangliang Zhu Yanli Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11541-11545
Developing molecules with high emission efficiency both in solution and the solid state is still a great challenge, since most organic luminogens are either aggregation‐caused quenching or aggregation‐induced emission molecules. This dilemma was overcome by integrating planar and distorted structures with long alkyl side chains to achieve DAπAD type emitters. A linear diphenyl–diacetylene core and the charge transfer effect ensure considerable planarity of these molecules in the excited state, allowing strong emission in dilute solution (quantum yield up to 98.2 %). On the other hand, intermolecular interactions of two distorted cyanostilbene units restrict molecular vibration and rotation, and long alkyl chains reduce the quenching effect of the π–π stacking to the excimer, eventually leading to strong emission in the solid state (quantum yield up to 60.7 %). 相似文献
994.
Yue Zhu Yujin Ji Zhengyu Ju Kang Yu Paulo J. Ferreira Yuanyue Liu Guihua Yu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17365-17369
Solvents play an essential role in many areas of chemistry and is the cornerstone of understanding reactivity in solution‐phase reactions. Solvent effects have been widely observed in intercalation reactions; however, understanding of the influence of solvents on the thermodynamics and kinetics remains largely elusive in intercalation chemistry. Now, the solvent‐dependent kinetics of ferrocene intercalation into a layered vanadyl phosphate (VOPO4?2 H2O) host is presented, with a special focus on primary alcohols. From methanol to 1‐hexnaol, the intercalation rate peaks in 1‐propanol (80 times faster than the slowest case in methanol). Similar kinetics of exfoliation are also found in these solvents without ferrocene. The correlation between intercalation and exfoliation is understood at atomic level by DFT calculations, which reveal the role of pre‐intercalated solvent molecules play in intralayer interactions, interlayer expansion, and layer sliding. 相似文献
995.
Shao‐Dong Su Xiao‐Quan Zhu Yue‐Hong Wen Lin‐Tao Zhang Yu‐Ying Yang Chen‐Sheng Lin Xin‐Tao Wu Tian‐Lu Sheng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15488-15492
An unusual tetra‐nuclear linear cyanido‐bridged complex [Ru2(μ‐ap)4‐CN‐Ru2(μ‐ap)4](BPh4) ( 1 ) (ap=2‐anilinopyridinate) has been synthesized and well characterized. The crystallographic data, magnetic measurement, IR, EPR and theoretical calculation results demonstrate that complex 1 is the first example of mixed spin Ru25+‐based complex with uncommon electronic configurations of S=1/2 for the cyanido‐C bound Ru25+ and S=3/2 for the cyanido‐N bound Ru25+. This phenomenon can be understood by the theoretical calculation results that from the precursor Ru2(μ‐ap)4(CN) (S=3/2) to complex 1 the energy gap between π* and δ* orbitals of the cyanido‐C bound Ru25+ core increases from 0.57 to 1.61 eV due to the enhancement of asymmetrical π back‐bonding effect, but that of the cyanido‐N bound Ru25+ core is essential identical (0.56 eV). Besides, the analysis of UV/Vis‐NIR spectra suggests that there exists metal to metal charge transfer (MMCT) from the cyanido‐N bound Ru25+ (S=3/2) to the cyanido‐C bound Ru25+ (S=1/2), supported by the TDDFT calculations. 相似文献
996.
Yue Yuan Zhiliang Wei Chengyan Chu Jia Zhang Xiaolei Song Piotr Walczak Jeff W. M. Bulte 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(43):15658-15663
The healthy prostate contains the highest concentration of mobile zinc in the body. As this level decreases dramatically during the initial development of prostate cancer, in vivo detection of prostate zinc content may be applied for diagnosis of prostate cancer. Using 19F ion chemical exchange saturation transfer magnetic resonance imaging (iCEST MRI) and TF‐BAPTA as a fluorinated Zn‐binding probe with micromolar sensitivity, we show that iCEST MRI is able to differentiate between normal and malignant prostate cells with a 10‐fold difference in contrast following glucose‐stimulated zinc secretion in vitro. The iCEST signal decreased in normal prostate cells upon downregulation of the ZIP1 zinc transporter. In vivo, using an orthotopic prostate cancer mouse model and a transgenic adenocarcinoma of the mouse prostate (TRAMP) model, a gradual decrease of >300 % in iCEST contrast following the transition of normal prostate epithelial cells to cancer cells was detected. 相似文献
997.
Yue Zhang Yue Zhang Guobin Song Yuling He Xiaobo Zhang Ying Liu Huangxian Ju 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(50):18375-18379
Stimulus‐responsive drug release possesses considerable significance in cancer therapy. This work reports an upconversion‐luminescence‐fueled DNA–azobenzene nanopump for rapid and efficient drug release. The nanopump is constructed by assembling the azobenzene‐functionalized DNA strands on upconversion nanoparticles (UCNPs). Doxorubicin (DOX) is loaded in the nanopump by intercalation in the DNA helix. Under NIR light, the UCNPs emit both UV and visible photons to fuel the continuous photoisomerization of azo, which acts as an impeller pump to trigger cyclic DNA hybridization and dehybridization for controllable DOX release. In a relatively short period, this system demonstrates 86.7 % DOX release. By assembling HIV‐1 TAT peptide and hyaluronic acid on the system, targeting of the cancer‐cell nucleus is achieved for perinuclear aggregation of DOX and enhanced anticancer therapy. This highly effective drug delivery nanopump could contribute to chemotherapy development. 相似文献
998.
Jiang Zhipeng Xie Fan Kang Chuanhong Wang Yanfei Yuan Long Wang Yue 《Journal of Radioanalytical and Nuclear Chemistry》2019,321(3):895-905
Journal of Radioanalytical and Nuclear Chemistry - Poly(cyclotriphosphazene-co-4,4′-diaminodiphenyl ether) microspheres (PZA) was based on hexachlorocyclotriphosphazene (HCCP) and... 相似文献
999.
利用密度泛函理论(DFT)研究了M12Ni(M=Pt, Sn, Cu) 3种双金属合金团簇的电子活性和结构稳定性, 并探讨了甲烷干法重整反应(DRM)在M12Ni双金属团簇表面的反应能量变化情况. 经比较发现甲烷脱氢和二氧化碳活化过程在Pt12Ni团簇表面进行需克服的活化能垒最低, 反应最易进行. Sn12Ni团簇上生成碳需要较高的活化能, 说明Sn12Ni团簇能够有效抑制焦碳的生成, 一定程度上克服了碳沉积导致的催化剂失活现象, 并且Sn12Ni团簇在C *和CH *氧化过程中表现出最佳的催化活性. Cu12Ni团簇仅在甲烷脱氢过程中表现出较为优异的催化活性. 相似文献
1000.
用NaOH溶液对高硅ZSM-5分子筛进行处理,考察其应用于苯-甲醇烷基化反应过程的最佳处理条件,并用XRD、SEM、XRF、NH3-TPD、TPO、BET等手段对试样进行表征。结果表明,NaOH在脱除分子筛硅物种的同时,也会脱出晶粒表面附着物,暴露出更多的酸性位,形成一定量的介孔,进而影响苯-甲醇烷基化性能。当NaOH处理量为2.4 mmol/gcat时,在液体积空速为85 h-1下,烷基化反应中苯的转化率达到38%,相比处理前提高了近16%,且积炭量低,稳定性好。 相似文献