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41.
Kenta Yamaguchi Dr. Toshinori Matsushima Dr. Atula S. D. Sandanayaka Yoko Homma Naoki Uchida Prof. Chihaya Adachi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(25):5598-5602
In organic light-emitting diodes (OLEDs) based on materials that show thermally activated delayed fluorescence (TADF), the internal quantum efficiency of 100 % can be obtained without using phosphorescence-based organometallics that contain rare metals. Therefore, with TADF-based emitters, it is possible to fabricate high-performing OLEDs at a lower cost. However, compared with fluorescence- and phosphorescence-based OLEDs, an understanding of degradation mechanisms in TADF-based OLEDs is still insufficient for future commercialization. In particular, it is widely recognized that the development of electron transport materials is crucial for improving OLED characteristics, especially driving voltages and operational durability. In this study, it was demonstrated that the operational durability of TADF-based OLEDs was greatly improved by introducing a triazine-based material of 2,4,6-tris(1,1′-biphenyl-4-yl)-[1,3,5]triazine (pT2T) as a hole-blocking layer (HBL) compared with a conventional HBL material of 2,4,6-tris(biphenyl-3-yl)-[1,3,5]triazine (T2T). Several experiments were carried out to make the reasons of the improved durability clearer, and attributed the improved durability to the shift of a carrier recombination zone from the emitting layer/HBL interface and the suppressed formation of excited-state quenchers in the pT2T HBL, because of the higher electron mobility of pT2T and the better stability of its radical anion state. 相似文献
42.
Nikolaos V. Tzouras Dr. Fady Nahra Dr. Laura Falivene Prof. Dr. Luigi Cavallo Marina Saab Prof. Dr. Kristof Van Hecke Dr. Alba Collado Dr. Christopher J. Collett Prof. Dr. Andrew D. Smith Prof. Dr. Catherine S. J. Cazin Prof. Dr. Steven P. Nolan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(20):4515-4519
We have been puzzled by the involvement of weak organic and inorganic bases in the synthesis of metal–N-heterocyclic carbene (NHC) complexes. Such bases are insufficiently strong to permit the presumed required deprotonation of the azolium salt (the carbene precursor) prior to metal binding. Experimental and computational studies provide support for a base-assisted concerted process that does not require free NHC formation. The synthetic protocol was found applicable to a number of transition-metal- and main-group-centered NHC compounds and could become the synthetic route of choice to form M–NHC bonds. 相似文献
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Newly established in 2018, the UK Research and Innovation (UKRI) strengthens the strategic coordination of the UK research and innovation system by bringing together seven Research Councils, Research England, and Innovate UK. Through its nine organizations, UKRI funds multidisciplinary and interdisciplinary research in a number of priority areas. It also runs the Strategic Priorities Fund to support multidisciplinary and interdisciplinary research in strategic areas identified by government policies as well as the Global Challenges Research Fund to promote challenge-led interdisciplinary research needed by developing countries. The UKRI makes significant efforts to engage stakeholders in the development, design, and implementation of multidisciplinary and interdisciplinary programs. It has also developed a range of mechanisms to improve the evaluation of multidisciplinary and interdisciplinary projects. Chinese science and innovation funding agencies could draw upon the UKRI experience from four aspects to advance interdisciplinary research in China. 相似文献
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Importing intramolecular hydrogen bond in phosphorescent transition metal complexes has been considered one of the excellent approaches to improve the electroluminescence performance of organic light-emitting diodes in real applications. However, the relationships between such H-bond structure and phosphorescent properties have not been theoretically revealed yet. In this study, two types of intramolecular hydrogen bonds are introduced into the two classes of traditional materials, that is, Pt(II) and Ir(III) complexes ( 1a and 2a ) to completely elucidate their influence on the structures and properties by comparing with the original phosphors ( 1b and 2b ) using density functional theory/time-dependent density functional theory for the first time. A comprehensive analysis of the geometric structures, molecular orbitals, and luminescence properties (including phosphorescence emission wavelengths and radiative and nonradiative decay processes) has been carried out. Our theoretical model highlights that complexes 1a and 2a embedded with H-bonds significantly promote the phosphorescence emission band blue-shifted and restrict molecular deformations compared with the corresponding 1b and 2b , which can provide helpful guidance to regulate and design several aspects of highly efficient blue phosphorescent emitters. 相似文献
47.
Zeinab Ahmadvand Mehdi Bayat Mohammad Ali Zolfigol 《Journal of computational chemistry》2020,41(26):C1-C1
Pd-PEPPSI type complexes are widely used as precatalyst in a variety of organic reactions, including the Negishi, Kumada and Suzuki-Miyaura cross-coupling reactions. The aim of this research is to determine potential proposed reaction pathways 1, 2, or 2′ (See Schemes 1 and S1–S4 ) for Pd-PEPPSI precatalyst activation in the presence of ethylene glycol as a solvent also in the gas phase at Cam-B3LYP-D3 method nominated among eight DFT methods examined. There is also investigation into the impact of promoter bases (NaOEt, NaOiPr, NaOtBu) on precatalyst activation of Pd-PEPPSI. Eventually, the most favorable proposed reaction pathway and promoter base for reducing Pd(II) to Pd(0) are predicted computationally. Notably, our findings are consistent with the organ Pd-PEPPSI type complexes that offer increased catalytic activity and provide basic information in the presence of solvents designing the monoligated Pd(0)-solvent. 相似文献
48.
The elementometalation process is a fundamental chemical step in several catalytic cycles. In this work, density functional theory computations have elucidated the detailed elementometalation mechanism of activated alkyne RCCR(RCO2Me) by Cp2TaH3 and rationalized the selectivity in experimental findings. The calculated results show that in the formation process of (E)-olefin monohydride((E)-Pro), the Gibbs free energy barrier is low and the entire reaction is spontaneous and exothermic; thus, (E)-Pro can be formed easily. The formation of (Z)-η2-olefin monohydride complex ((Z)-Pro) is difficult due to its high Gibbs free energy barrier. The formation process (E)-Pro consists of the following five steps: hydride H1-shift, conformational isomerism 1, hydride H2-shift, conformational isomerism 2, and olefin coordination process. Topological analysis shows that there is a five-membered ring plane structure in the reaction pathway and that the final product (E)-Pro belongs to a typical η2-olefin monohydride complex. Our calculated results provide an explanation for experimental observations and useful insights for further development of olefin functionalization. © 2019 Wiley Periodicals, Inc. 相似文献
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50.
Xinfeng Zhu Yanli Mao Hongpan Liu Haiyan Kang Biao Liu Zhongxian Song Xueping Liu Yifei Guo Huixian Du Qiulin Zhang 《应用有机金属化学》2020,34(2):e5285
FeOx, TiO2, and Fe–Ti–Ox catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–Ox catalyst. TiO2 rutile was detected over TiO2, but not over Fe–Ti–Ox, which suggested that the interaction between Fe and Ti species could inhibit the TiO2 phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–Ox could promote the selectivity of NH3 and CO. The mechanism of hydrolysis of HCN over FeOx, TiO2, and Fe–Ti–Ox can be given as follows: HCN + H2O → methanamide → ammonium formate → formic acid → H2O + CO. 相似文献