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81.
采用联苯二酐与3种含酰胺结构二胺制备了具有不同取代基团的聚酰胺-酰亚胺薄膜, 考察了酰胺结构对薄膜力学、 耐热及尺寸稳定性的影响, 研究了聚集态结构与薄膜热膨胀行为的关系和规律. 该系列薄膜具有超高强度和优异的耐热性能, 拉伸强度高达280.5 MPa, 玻璃化转变温度在389~409 ℃, 并在30~300 ℃温度范围内表现出超低负膨胀, 热膨胀系数(CTE, ppm/℃, 即10 6 cm·cm -1·℃ -1)在-3.05~-1.74 ppm/℃之间. 聚集态分析结果表明, 酰胺结构使分子链间形成了强氢键相互作用, 分子链在薄膜面内方向高度有序取向, 并在膜厚方向堆积更为紧密, 使薄膜表现出热收缩现象. 通过不同体积大小的取代基团进一步调控分子链间相互作用及排列堆积, 可实现薄膜在高温下近乎零尺寸形变, 为设计制备超低膨胀聚合物基板材料提供了新思路. 相似文献
82.
Minlang Yang Dr. In Seob Park Yasuhiro Miyashita Katsunori Tanaka Prof. Dr. Takuma Yasuda 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(33):14059-14065
Herein, the universal design of high-efficiency stimuli-responsive luminous materials endowed with mechanochromic luminescence (MCL) and thermally activated delayed fluorescence (TADF) functions is reported. The origin of the unique stimuli-triggered TADF switching for a series of carbazole–isophthalonitrile-based donor–acceptor (D–A) luminogens is demonstrated based on systematic photophysical and X-ray analysis, coupled with theoretical calculations. It was revealed that a tiny alteration of the intramolecular D–A twisting in the excited-state structures governed by the solid morphologies is responsible for this dynamic TADF switching behavior. This concept is applicable to the fabrication of bicolor emissive organic light-emitting diodes using a single TADF emitter. 相似文献
83.
Mengmeng Zhang Dr. Jiajun Wang Hui Xue Dr. Jinfeng Zhang Prof. Dr. Shengjie Peng Dr. Xiaopeng Han Prof. Dr. Yida Deng Prof. Dr. Wenbin Hu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18621-18625
Cu2O is a typical photoelectrocatalyst for sustainable hydrogen production, while the fast charge recombination hinders its further development. Herein, Ni2+ cations have been doped into a Cu2O lattice (named as Ni-Cu2O) by a simple hydrothermal method and act as electron traps. Theoretical results predict that the Ni dopants produce an acceptor impurity level and lower the energy barrier of hydrogen evolution. Photoelectrochemical (PEC) measurements demonstrate that Ni-Cu2O exhibits a photocurrent density of 0.83 mA cm−2, which is 1.34 times higher than that of Cu2O. And the photostability has been enhanced by 7.81 times. Moreover, characterizations confirm the enhanced light-harvesting, facilitated charge separation and transfer, prolonged charge lifetime, and increased carrier concentration of Ni-Cu2O. This work provides deep insight into how acceptor-doping modifies the electronic structure and optimizes the PEC process. 相似文献
84.
Dr. Shaomin Peng Dr. Qi Wei Dr. Bingzhe Wang Dr. Zhipeng Zhang Hongcheng Yang Guotao Pang Prof. Kai Wang Prof. Guichuan Xing Prof. Xiao Wei Sun Prof. Zikang Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22340-22346
Quasi-two-dimensional (2D) perovskites are promising candidates for light generation owing to their high radiative rates. However, strong exciton–phonon interactions caused by mechanical softening of the surface act as a bottleneck in improving their suitability for a wide range of lighting and display applications. Moreover, it is not easily available to tune the phonon interactions in bulk films. Here, we adopt bottom-up fabricated blue emissive perovskite nanoplatelets (NPLs) as model systems to elucidate and as well as tune the phonon interactions via engineering of binary NPL solids. By optimizing component domains, the phonon coupling strength can be reduced by a factor of 2 driven by the delocalization of 2D excitons in out-of-plane orientations. It shows the picosecond energy transfer originated from the Förster resonance energy transfer (FRET) efficiently competes with the exciton–phonon interactions in the binary system. 相似文献
85.
We present a facile and efficient method for modifying the surface of silica-coated Fe3O4 magnetic nanoparticles (MNPs) with bis(pyrazolyl) triazine ruthenium(II) complex [ MNPs@BPT–Ru (II) ] . Field emission-scanning electron microscopy, thermogravimetric/derivative thermogravimetry analysis, X-ray powder diffraction, Fourier-transform infrared spectroscopy, vibrating sample magnetometry, and energy-dispersive X-ray spectrometry analyses were employed for characterizing the structure of these nanoparticles. MNPs@BPT–Ru(II) nanoparticles proved to be a magnetic, reusable, and heterogeneous catalyst for the hydrogen transfer reduction of ketone derivatives. In addition, highly pure products were obtained with excellent yields in relatively short times in the presence of this catalyst. A comparison of this catalyst with those previously used for the hydrogen transfer reactions proved the uniqueness of MNPs@BPT–Ru(II) nanoparticle which is due to its inherent magnetic properties and large surface area. The presented method also had other advantages such as simple reaction conditions, eco-friendliness, high recovery ability, easy work-up, and low cost. 相似文献
86.
Milad Kazemnejadi Seyyedeh Ameneh Alavi G. Zinat Rezazadeh Mohammad Ali Nasseri Ali Allahresani Mohsen Esmaeilpour 《应用有机金属化学》2020,34(2):e5388
Cu(II) Schiff base complex supported on Fe3O4@SiO2 nanoparticles was employed as a magnetic nanocatalyst (nanocomposite) with a phase transfer functionality for the one-pot preparation of α-aminonitriles (Strecker reaction). The desired α-aminonitriles were obtained from the reaction of aromatic or aliphatic aldehydes, aniline or benzyl amine, NaCN, and 1.6 mol% of the catalyst in water at room temperature and good to excellent yields were obtained for all substrates. The catalyst was characterized analytically and instrumentally including Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric, nuclear magnetic resonance, energy-dispersive X-ray spectroscopy, inductively coupled plasma spectroscopy, vibrating-sample magnetometry analysis, dynamic light scattering, Brunauer–Emmett–Teller surface area, field emission scanning electron microscopy, and transmission electron microscopy analyses. The reaction mechanism was investigated, in which the performance of the catalyst as a phase transition factor seems to be probable. The catalyst showed high activity, high turnover frequency (TOF)s, significant selectivity, and fast performance toward the Strecker synthesis. The nanocatalyst can be readily and quickly separated from the reaction mixture with an external magnet and can be reused for at least seven successive reaction cycles without significant reduction in efficiency. 相似文献
87.
Dan-Dan Wang Li Song You-Yu Wang Jia-Yu Guo Hang-Yan Shen Xiao-Rong Wang Wen-Xiang Chai 《应用有机金属化学》2020,34(4):e5561
Four new heteroleptic [Cu(NN)P2]+-type cuprous complexes— 1 -TPP, 2 -POP, 3 -Xantphos, and 4 -DPPF—were designed and synthesized using a diimine ligand 2-(2′-pyridyl)benzoxazole (2-PBO) and different phosphine ligands (TPP, triphenylphosphine; POP, bis[2-(diphenylphosphino)phenyl]ether; Xantphos, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; DPPF, 1,1′-bis(diphenylphosphino)-ferrocene). All complexes were characterized using single-crystal X-ray diffraction, spectroscopic analysis (infrared, UV–Vis.), elemental analysis, and photoluminescence (PL). Single-crystal X-ray diffraction revealed complexes 1 – 4 as isolated cation complex structures with a tetrahedral CuN2P2 coordination geometry and diverse P–Cu–P angles. Their UV–Vis. absorption spectra exhibited a blue-shift sequence in wavelength with an enlarged P–Cu–P angle from 4 to 2 then to 3 and then to 1 . The PL emission peaks of 1 – 3 also exhibited a similar blue-shift sequence ( 2 → 3 → 1 ). Their PL lifetime in microseconds (~7.5, 5.1, and 4.7 μs for 1 , 2 , and 3 , respectively) indicated that their PL behavior represents phosphorescence. Time-dependent density functional theory (TD-DFT) calculation and wavefunction analysis revealed that S1 and T1 states of 1 – 3 should be assigned as metal–ligand and ligand–ligand charge-transfer (ML + L'L)CT states. Their UV–Vis. absorption and phosphorescence should be attributed to the charge transfer from the P–Cu–P segment to the 2-PBO ligand. Therefore, as the P–Cu–P angle increased (lower HOMO), the energy of S1 and T1 states also increased, following the change of PL color. 相似文献
88.
89.
Dr. Josh Abbenseth Dr. Florian Wätjen Dr. Markus Finger Prof. Dr. Sven Schneider 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(52):23780-23784
The utilization of monomeric, lower phosphorous oxides and oxoanions, such as metaphosphite (PO2−), which is the heavier homologue of the common nitrite anion but previously only observed in the gas phase and by matrix isolation, requires new synthetic strategies. Herein, a series of rhenium(I–III) complexes with PO2− as ligand is reported. Synthetic access was enabled by selective oxygenation of a terminal phosphide complex. Spectroscopic and computational examination revealed slightly stronger σ-donor and comparable π-acceptor properties of PO2− compared to homologous NO2−, which is one of the archetypal ligands in coordination chemistry. 相似文献
90.
Previously, master equation (ME) simulations using semiclassical transition state theory (SCTST) and high-accuracy extrapolated ab initio thermochemistry (HEAT) predicted rate constants in excellent agreement with published experimental data over a wide range of pressure and temperatures ≳250 K, but the agreement was not as good at lower temperatures. Possible reasons for this reduced performance are investigated by (a) critically evaluating the published experimental data and by investigating; (b) three distinct ME treatments of angular momentum, including one that is exact at the zero- and infinite-pressure limits; (c) a hindered-rotor model for HOCO that implicitly includes the cis- and trans-conformers; (d) possible empirical adjustments of the thermochemistry; (e) possible empirical adjustments to an imaginary frequency controlling tunneling; (f) including or neglecting the prereaction complex PRC1; and (g) its possible bimolecular reactions. Improvements include better approximations to factors in SCTST and using the Hill and van Vleck treatment of angular momentum coupling. Evaluation of literature data does not reveal any specific shortcomings, but the stated uncertainties may be underestimated. All ME treatments give excellent fits to experimental data at T ≥ 250 K, but the discrepancy at T < 250 K persists. Note that each ME model requires individual empirical energy transfer parameters. Thermochemical adjustments were unable to match the experimental H/D kinetic isotope effects. Adjusting an imaginary frequency can achieve good fits, but the adjustments are unacceptably large. Whether PRC1 and its possible bimolecular reactions are included had little effect. We conclude that none of the adjustments is an improvement over the unadjusted theory. Note that only one set of experimental data exists in the regime of the discrepancy with theory, and data for DO + CO are scanty. 相似文献