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11.
Dr. Jordan Donat Mr. Patrick Dubourdeaux Dr. Martin Clémancey Dr. Julia Rendon Clara Gervasoni Mr. Morgan Barbier Jessica Barilone Dr. Jacques Pécaut Prof. Dr. Serge Gambarelli Prof. Dr. Pascale Maldivi Prof. Dr. Jean-Marc Latour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202201875
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor. 相似文献
12.
13.
This work presents a scalable approach for preparing spherical hollow mesoporous silica with high surface area/pore volume, serving as outstanding support for supported phosphotungstic acid catalyst with much superior catalytic performance to the one on previously reported spherical mesoporous silica toward diverse transformations, ascribed to the strengthened mass transfer and the enlarged exposure degree of acidic sites to reactants those resulting from unique hollow and mesoporous morphology. 相似文献
14.
Dr. Antony J. Stasyuk Dr. Olga A. Stasyuk Prof. Dr. Miquel Solà Prof. Dr. Alexander A. Voityuk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(10):2577-2585
Porphyrin–fullerene dyads are promising candidates for organic photovoltaic devices. The electron-transfer (ET) properties of the molecular devices depend significantly on the mutual position of the donor and acceptor. Recently, a new type of molecular isomerism (akamptisomerism) has been discovered. In the present study, we explore how photoinduced ET can be modulated by passing from one akamptisomer to another. To this aim, four akamptisomers of the quinoxalinoporphyrin–[60]fullerene complex are selected for computational study. The most striking finding is that, depending on the isomer, the porphyrin unit in the dyad can act as either electron donor or electron acceptor. Thus, the stereoisomeric diversity allows one to change the direction of ET between the porphyrin and fullerene moieties. To understand the effect of akamptisomerism on the photoinduced ET processes, a detailed analysis of initial and final states involved in the ET is performed. The computed rate for charge separation is estimated to be in the region of 1–10 ns−1. The formation of a long-living quinoxalinoporphyrin anion radical species is predicted. 相似文献
15.
Chunhong Wang Qi Cui Zhixin Zhang Prof. Zhu-Jun Yao Dr. Shaozhong Wang Prof. Zhi-Xiang Yu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9821-9826
1,3-Azaprotio transfer of propargylic α-ketocarboxylate oximes, a new type of alkynyl oximes featuring an ester tether, has been explored by taking advantage of gold catalysis. The incorporation of an oxygen atom to the chain of alkynyl oximes led to the formation of two different oxa-cyclic nitrones. It was found that internal alkynyl oximes with an E-configuration deliver five-membered nitrones, whereas terminal alkynyl oximes with an E-configuration afford six-membered nitrones. DFT calculations on four possible pathways supported a stepwise formation of C−N and C−H bonds, in which a 1,3-acyloxy-migration competes with the 1,3-azaprotio-transfer, especially in the case of internal alkynyl oximes. The relative nucleophilic properties of oxygen in the carbonyl group and the nitrogen in the oxime, the electronic effects of alkynes, and the influence of the ring system have been investigated computationally. 相似文献
16.
采用SST k-w低雷诺数湍流模型对加热条件下超临界压力CO2在内径di=22.14 mm,加热长度Lh=2440 mm水平圆管内三维稳态流动与传热特性进行了数值计算.通过超临界CO2在水平圆管内的流动传热实验数据验证了数值模型的可靠性和准确性.首先,研究了超临界压力CO2在水平圆管内的流动传热特点,基于超临界CO2在类临界温度Tpc处发生类液-类气“相变”的假设,揭示了水平圆管顶母线和底母线区域不同的流动传热行为.然后,分析了热流密度qw和质量流速G对水平圆管内超临界压力CO2流动换热的影响,通过获取流体域内的物性分布、速度分布和湍流分布等详细信息,重点解释了不同热流密度qw和质量流速G下顶母线内壁温度Tw,i分布产生差异的传热机理,分析结果确定了类气膜厚度d、类气膜性质、轴向速度u和湍动能k是影响顶母线壁温分布差异的主要因素.研究结果可以为超临界压力CO2换热装置的优化设计和安全运行提供理论指导. 相似文献
17.
Electron transfer reactions are the most important processes at electrochemical interfaces. They are determined by the interplay between the interaction of the reactant with the solvent and the electronic levels of the electrode surface. Theoretical treatments only based on Density Functional Theory calculations are not sufficient. This review emphasizes mainly the effect of the electronic structure of the electrode material on electron transfer under different kinetic regimes. Our goal is to understand experimental results in the framework of a theory valid for arbitrary strengths of electronic coupling. 相似文献
18.
《Current Applied Physics》2020,20(1):49-57
In this work, we report a new method for extending the response spectra of organic photodetectors (OPDs) by incorporating PBDT-TT-C and PBDT-TT-F in the P3HT:PC61BM. The effects of PBDT-TT-C and PBDT-TT-F incorporation on the optical and electrical properties of OPDs were investigated, It was found that when the mass ratio of P3HT:PBDT-TT-F:PBDT-TT-C:PC61BM was 12:2:2:8, the response spectrum of the active layer was extended to 780 nm. The responsivity (R) and external quantum efficiency (EQE) of the OPDs reached 340, 376, 315 mA/W and 67%, 88%, 85% under 630, 530, and 460 nm illumination and −1 V bias, respectively, and the detectivity (D*) reached 1012 Jones. The results show that the inclusion of an appropriate amount of donor material with similar chemical structure and complementary absorption spectrum can reduce the influence of the doping material on the micro-morphology of the original film while improving the absorption of the spectrum. The interaction between the donor materials promotes the generation of photogenerated carriers and increases the photocurrent of the OPDs. In addition, the incorporation of the different component promotes crystallization of the film, resulting in a reduction in dark current of the OPDs. 相似文献
19.
《Current Applied Physics》2020,20(9):1073-1079
We study emissivity (ε)-dependent radiative heat transfer phenomena in remote and contact configurations. To demonstrate the emissivity-dependent radiative heating mode in a remote configuration, we fabricated miniature greenhouses covered with low (0.34)- and high-ε (0.86) polyethylene films and monitored temperatures on the floors, insides, and covers of the greenhouses during 24 h. The high-ε greenhouse yielded a 9-°C increase in floor temperature relative to the low-ε greenhouse at a one-sun solar irradiance because the high-ε film effectively trapped floor radiation. In contrast, the cover temperature remained lower in the high-ε greenhouse due to intensified radiation released from the high-ε film. This self-cooling effect was more evident when an emissive film was in physical contact with an object. While bare copper heated up to 55 °C, a high-ε film coated copper substrate was kept cooler by 4 and 2 °C compared with the bare and low-ε film coated copper samples, respectively. 相似文献
20.
Dr. Simon Pascal Léo Bucher Dr. Nicolas Desbois Dr. Christophe Bucher Dr. Chantal Andraud Prof. Dr. Claude P. Gros 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4971-4979
The synthesis of dyad and triad aza‐BODIPY‐porphyrin systems in two steps starting from an aryl‐substituted aza‐BODIPY chromophore is described. The properties of the resulting aza‐BODIPY‐porphyrin conjugates have been extensively investigated by means of electrochemistry, spectroelectrochemistry, and absorption/emission spectroscopy. Fluorescence measurements have revealed a dramatic loss of luminescence intensity, mainly due to competitive energy transfer and photoinduced electron transfer involving charge separation followed by recombination. 相似文献