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排序方式: 共有243条查询结果,搜索用时 15 毫秒
31.
Ziqi Zhu Di Zhang Tongtong Xiao Yu-Hui Fang Xiao Xiao Xiao-Ge Wang Prof. Shang-Da Jiang Prof. Dahui Zhao 《Angewandte Chemie (International ed. in English)》2023,62(49):e202314900
Stable carbon-based polyradicals exhibiting strong spin-spin coupling and slow depolarization processes are particularly attractive functional materials. A new molecular motif synthesized by a convenient method that allows the integration of stable, high-spin radicals to (hetero)aromatic polycycles has been developed, as illustrated by a non-Kekulé diradical showing a triplet ground state with long persistency (τ1/2≈31 h) in air. Compared to the widely used 1,3-phenylene, the newly designed (diaza)pyrene-4,10-diyl moiety is for the first time demonstrated to confer ferromagnetic (FM) spin coupling, allowing delocalized non-disjoint SOMOs. With the X-ray crystallography unambiguously proving the diradical structure, the triplet ground state was thoroughly characterized. A large ΔES-T of 1.1 kcal/mol, proving the strong FM coupling effect, was revealed consistently by superconducting quantum interference device (SQUID) measurements and variable-temperature electron paramagnetic resonance (EPR) spectroscopy, while the zero-field splitting and triplet nutation characters were examined by continuous-wave and pulsed EPR spectroscopy. A millisecond spin-lattice relaxation time was also detected. The current study not only offers a new molecular motif enabling FM coupling between carbon-based spins, but more importantly presents a general method for installing stable polyradicals into functional π-systems. 相似文献
32.
The demand for practical methods for the synthesis of novel fluoroalkyl molecules is increasing owing to their diverse applications. Our group has achieved efficient difunctionalizing fluoroalkylations of alkenes using fluorinated carboxylic anhydrides as user-friendly fluoroalkyl sources. Fluorinated diacyl peroxide, prepared in situ from carboxylic anhydrides, enables the development of novel reactions when used as a radical fluoroalkylating reagent. In this account, we aim to provide an in-depth understanding of the structure, bonding, and reactivity of fluorinated diacyl peroxides and radicals as well as their control in fluoroalkylation reactions. In the first part of this account, the physical properties and reactivity of diacyl peroxides and fluoroalkyl radicals are described. In the subsequent part, we categorize the reactions into copper-catalyzed and metal-free methods utilizing the oxidizing properties of fluorinated diacyl peroxides. We also outline examples and mechanisms. 相似文献
33.
Philippe Renaud Michle Gerster 《Angewandte Chemie (International ed. in English)》1998,37(19):2562-2579
The neglect of free radicals over the past few years has been overcome, and they are no longer only considered as interesting reactive intermediates with limited synthetic potential. New opportunities are opened up by performing radical reactions in the presence of Lewis acids. Rate enhancement of radical addition to olefins as well as stereochemical control of such reactions can be achieved in a unique manner. Recent examples of enantioselective radical reactions and perspectives for applications in catalysis are discussed. 相似文献
34.
Hiroyuki Nishide Makoto Miyasaka Eishun Tsuchida 《Angewandte Chemie (International ed. in English)》1998,37(17):2400-2402
An average spin quantum number of 7/2 is displayed by the star-shaped, π-conjugated polyradical 1 , even with a spin concentration of 0.8 per monomer unit. Polymer 1 is stable at room temperature, and it is a powerful candidate for the synthesis of a feasible polymer with very high spin. 相似文献
35.
检测活性氧的荧光探针新进展 总被引:1,自引:0,他引:1
活性氧对于人体是十分重要的。然而,过量的活性氧是相当有害的,它们会对人体产生氧化损伤,导致细胞死亡。活性氧现在已经引起了化学、生物、医药等多个领域学者的浓厚兴趣,它们被认为和多种病理条件有密切的联系。由于活性氧寿命短、反应活性高,并且大部分都存在于体内很难被捕获,因此它们的分析测定是一项国际性难题。荧光探针作为活性氧的高灵敏的检测分析物,已经得到越来越广泛和深入的研究。由于每一种活性氧都有它独特的生理学活性,因此设计高选择性的,能够检测具体一种活性氧的荧光探针分子就显得十分重要。本文主要对近三年来检测单线态氧、过氧化氢、超氧阴离子和羟自由基这四种活性氧的荧光探针的研究进展进行综述,关注这类荧光探针的检测机理以及具体应用。 相似文献
36.
An improved set of molecular constants and term values are given for the X2Π (v = 0–13) and B2Σ+ (v = 0 and 1) states of the OH radical. They are derived from a fit of previously published laboratory data and additional lines taken from infrared solar spectra recorded on orbit. 相似文献
37.
M. Liu T. Pauchard M. Sjdin O. Launila P. van der Meulen L.-E. Berg 《Journal of Molecular Spectroscopy》2009,257(1):105-107
A time-resolved experiment on the A2Π state of gaseous calcium hydride has been performed by applying laser spectroscopic methods. The following zero-pressure lifetime was obtained for the CaH A2Π state: τυ´=0 = 33.2 (±3.2) ns and τυ´=1 = 33.7 (±5.2) ns. The lifetime was found to be the same for the A2Π½ and A2Π3/2 states. 相似文献
38.
Guy Yardeni Israel Zilbermann Eric Maimon Haim Cohen Dan Meyerstein 《Research on Chemical Intermediates》2009,35(4):543-554
A new CeIII complex was synthesized by mixing the ligand “dioxocyclam” with CeIII ions at pH 8.0 and its redox properties were investigated.
相似文献
Dan Meyerstein (Corresponding author)Email: |
39.
The study presents the characterization of a novel variable frequency (11–50 kHz) Atmospheric Pressure Plasma Jet (APPJ) source and comparison of the results with 13.56 MHz source, in terms of species generation and species temperature. The behavior of variable frequency APPJ at different frequency regimes was investigated using optical emission spectroscopy to understand the interaction with the ambient environment. The quantitative dependence of the radical generation on driving frequency and time of treatment was also analyzed by direct synthesis of H2O2 by plasma-water interaction. The plasma formed with a kHz driving frequency had a low treatment temperature, which was suitable for biological species, but the plasma generated with a 13.56 MHz driving frequency had a substantially higher radical density than the kHz plasma. As a result, the APPJ device's ability to tune the radical density and treatment temperature with a change in kHz frequency has been demonstrated. 相似文献
40.