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991.
Qihao Wu Song‐Wei Li Heng Xu Hong Wang Pei Hu Hao Zhang Cheng Luo Kai‐Xian Chen Bastien Nay Yue‐Wei Guo Xu‐Wen Li 《Angewandte Chemie (International ed. in English)》2020,59(29):12105-12112
Placobranchus ocellatus is well known to produce diverse and complex γ‐pyrone polypropionates. In this study, the chemical investigation of P. ocellatus from the South China Sea led to the discovery and identification of ocellatusones A–D, a series of racemic non‐γ‐pyrone polyketides with novel skeletons, characterized by a bicyclo[3.2.1]octane ( 1 , 2 ), a bicyclo[3.3.1]nonane ( 3 ) or a mesitylene‐substituted dimethylfuran‐3(2H)‐one core ( 4 ). Extensive spectroscopic analysis, quantum chemical computation, chemical synthesis, and/or X‐ray diffraction analysis were used to determine the structure and absolute configuration of the new compounds, including each enantiomer of racemic compounds 1 – 4 after chiral HPLC resolution. An array of new and diversity‐generating rearrangements is proposed to explain the biosynthesis of these unusual compounds based on careful structural analysis and comparison with six known co‐occurring γ‐pyrones ( 5 – 10 ). Furthermore, the successful biomimetic semisynthesis of ocellatusone A ( 1 ) confirmed the proposed rearrangement through an unprecedented acid induced cascade reaction. 相似文献
992.
Hui Wang Changcheng Jing Adam Noble Varinder Kumar Aggarwal 《Angewandte Chemie (International ed. in English)》2020,59(39):16859-16872
The stereospecific 1,2‐migration of boronate complexes is one of the most representative reactions in boron chemistry. This process has been used extensively to develop powerful methods for asymmetric synthesis, with applications spanning from pharmaceuticals to natural products. Typically, 1,2‐migration of boronate complexes is driven by displacement of an α‐leaving group, oxidation of an α‐boryl radical, or electrophilic activation of an alkenyl boronate complex. The aim of this article is to summarize the recent advances in the rapidly expanding field of electrophile‐induced stereospecific 1,2‐migration of groups from boron to sp2 and sp3 carbon centers. It will be shown that three different conceptual approaches can be utilized to enable the 1,2‐migration of boronate complexes: stereospecific Zweifel‐type reactions, catalytic conjunctive coupling reactions, and transition metal‐free sp2–sp3 couplings. A discussion of the reaction scope, mechanistic insights, and synthetic applications of the work described is also presented. 相似文献
993.
Polycyclic saturated hydrocarbons (PSHs) are attractive candidates as hydrocarbon propellants. To assess their potential values, one of the key factors is to determine their energy contents, such as to calculate their heats of formation (HOF). In this work, we have calculated HOFs for a set of 36 PSHs including exo-Tricyclo[5.2.1.0(2,6)] decane, the principal component of the high-energy density hydrocarbon fuel commonly identified as JP-10. The results from B3LYP, B3LYP-D3BJ, M06-2X, B2PLYP, B2PLYP-D3BJ, and the XYG3 type of doubly hybrid (xDH) functionals are presented. It is demonstrated here that the xDH functionals yield accurate HOFs in good agreement with those from experiments or the G4 theory. In particular, XYGJ-OS, a low scaling xDH functional, is shown to hold the promise for accurate prediction of HOFs for PSHs of larger sizes. © 2018 Wiley Periodicals, Inc. 相似文献
994.
Development of eco‐friendly, cost‐effective, and high‐performance electrocatalysts to replace precious metal platinum for oxygen reduction reaction (ORR) has received increasing attention. Herein, we adopt a facile one‐pot strategy to embed Cu nanoparticles onto N‐doped carbon‐graphene (Cu@NC‐700). The Cu@NC‐700 exhibits robust and efficient ORR catalysis with positive half‐wave potential (~0.86 V vs. RHE) and low Tafel slope (33.9 mV?dec–1) in 0.1 M KOH solution. Meanwhile, it manifests remarkable electrochemical stability, and strong tolerance to methanol crossover and carbon monoxide poisoning. The synergistic effect between Cu‐N‐C sites, Cu nanoparticles, and N‐doped carbon support speeds up ORR electrocatalysis. 相似文献
995.
H. L. Wu C. P. Wang H. Zhang H. P. Peng F. Wang 《Russian Journal of Coordination Chemistry》2016,42(3):170-177
The reactions of copper(II) nitrate with 3-oxapentane-1,5-diamine (Oda) were investigated under different molar ratio. In the case of a 1: 1 molar ratio of copper(II) nitrate and Oda, the mononuclear complex [Cu(Oda)(NO3)2] (I) was obtained. In contrast, the treatment of copper(II) nitrate with twice Oda afforded inorganic polymer {[Cu(μ-Oda)(Oda)] · (NO3)2} n (II). The molecular structures of the two new complexes were determined from the elemental analyses, IR spectra and single-crystal X-ray diffraction (CIF files CCDC nos. 828193 (I) and 828018 (II)). Two Cu(II) complexes were both five-coordinated and forming a distorted square-base pyramidal geometry. Two complexes are stabilized by the intermolecular hydrogenbond. 相似文献
996.
997.
Chong Wu Jiang-Lin Zhao Xue-Kai Jiang Xin-Long Ni Xi Zeng Carl Redshaw Takehiko Yamato 《Analytica chimica acta》2016
A new type of chemosensor-based approach to the detection of 2,4,6-trinitrophenol (TNP) is described in this paper. Two hexahomotrioxacalix[3]arene-based chemosensors 1 and 2 were synthesized through click chemistry, which exhibited high binding affinity and selectivity toward TNP as evidenced by UV–vis and fluorescence spectroscopy studies. 1H NMR titration analysis verified that CH?O hydrogen bonding is demonstrated as the mode of interaction, which possibly facilitates effective charge-transfer. 相似文献
998.
Yanying Wang Xiangyang Yu Xiaoxue Ye Kangbing Wu Tsunghsueh Wu Chunya Li 《Analytica chimica acta》2016
Gold nanorods (AuNRs) integrated with ZnCdHgSe near-infrared quantum dots (AuNRs-ZnCdHgSe QDs) were successfully synthesized and characterized by transmission electron microscope, X-ray photoelectron spectroscopy, and X-ray diffraction. A glassy carbon electrode was decorated with the aforementioned AuNRs-ZnCdHgSe QDs nanocomposite, which provides a biocompatible interface for the subsequent immobilization of prostate specific antibody (anti-PSA). After being successively treated with glutaraldehyde vapor and bovine serum albumin solution, a photoelectrochemical immunosensing platform based on anti-PSA/AuNRs-ZnCdHgSe QDs/GCE was established. The photocurrent response of ZnCdHgSe QDs was tremendously improved by AuNRs due to the effect of resonance energy transfer which can be deduced from the dependence of the enhanced efficiency on the AuNRs with different length-to-diameter ratios and spectral absorption characteristics. A maximum photocurrent was obtained when the absorption spectrum of AuNRs matched well with the emission spectrum of ZnCdHgSe QDs. A photoelectrochemical immunosensor for prostate specific antigen (PSA) was achieved by monitoring the photocurrent variation. The photocurrent variation before and after being interacted with PSA solution exhibits a good linear relationship with the logarithm of its concentration (logcPSA) in the range from 1.0 pg mL−1 to 50.0 ng mL−1. The detection limit of this photoelectrochemical immunosensor is able to reach 0.1 pg mL−1 (S/N = 3). Determining PSA in clinical human serum was also demonstrated by using the developed anti-PSA(BSA)/AuNRs-ZnCdHgSe QDs/GCE electrode. The results were comparable with those obtained from an enzyme-linked immunosorbent assay method. 相似文献
999.
Xiaoqing Liang Xue Wu Xiaoming Huang Yan Su Jun Hu Jijun Zhao 《Journal of Cluster Science》2016,27(3):935-946
We employ a noncollinear implementation of density functional theory (DFT) including spin–orbit coupling (SOC) interaction to calculate the magnetic properties of Irn (n = 2–5) clusters. The impact of the magnetic anisotropy on the geometric structures and magnetic properties has been analyzed. SOC leads to formation of large orbital moment and a mixing of different spin states, but does not affect the relative stability of different structural isomers for a given cluster. In order to measure the SOC effect, we further define the spin–orbit energy (Eso) and compute the exact values. Magnetic anisotropy energies (MAEs) obtained from DFT calculations are further supported by the results of torque approach. We find that MAEs of Ir2 and Ir3 in ground state configurations are 40.6 and 28.5 meV respectively, while the MAE decreases to 9 meV for Ir4. For Ir5, MAE for its ground state structure increases to 38.3 meV. 相似文献
1000.
Hydrogen Treatment for Superparamagnetic VO2 Nanowires with Large Room‐Temperature Magnetoresistance 下载免费PDF全文
Zejun Li Yuqiao Guo Prof. Zhenpeng Hu Jihu Su Jiyin Zhao Junchi Wu Jiajing Wu Yingcheng Zhao Prof. Changzheng Wu Prof. Yi Xie 《Angewandte Chemie (International ed. in English)》2016,55(28):8018-8022
One‐dimensional (1D) transition metal oxide (TMO) nanostructures are actively pursued in spintronic devices owing to their nontrivial d electron magnetism and confined electron transport pathways. However, for TMOs, the realization of 1D structures with long‐range magnetic order to achieve a sensitive magnetoelectric response near room temperature has been a longstanding challenge. Herein, we exploit a chemical hydric effect to regulate the spin structure of 1D V–V atomic chains in monoclinic VO2 nanowires. Hydrogen treatment introduced V3+ (3d2) ions into the 1D zigzag V–V chains, triggering the formation of ferromagnetically coupled V3+–V4+ dimers to produce 1D superparamagnetic chains and achieve large room‐temperature negative magnetoresistance (?23.9 %, 300 K, 0.5 T). This approach offers new opportunities to regulate the spin structure of 1D nanostructures to control the intrinsic magnetoelectric properties of spintronic materials. 相似文献