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排序方式: 共有113条查询结果,搜索用时 18 毫秒
41.
Dr. Dachang Bai Yanjiang Yu Prof. Dr. Haiming Guo Prof. Dr. Junbiao Chang Prof. Dr. Xingwei Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(7):2762-2766
Ni0-catalyzed chemo- and enantioselective [3+2] cycloaddition of cyclopropenones and α,β-unsaturated ketones/imines is described. This reaction integrates C−C bond cleavage of cyclopropenones and enantioselective functionalization by carbonyl/imine group, offering a mild approach to γ-alkenyl butenolides and lactams in excellent enantioselectivity (88–98 % ee) through intermolecular C−C activation. 相似文献
42.
Zetong Ma Zhiqiang Yang Lan Mu Lisong Deng Liangjian Chen Bohan Wang Xianfeng Qiao Dehua Hu Bing Yang Dongge Ma Junbiao Peng Yuguang Ma 《Chemical science》2021,12(44):14808
Manipulating the molecular orbital properties of excited states and the subsequent relaxation processes can greatly alter the emission behaviors of luminophores. Herein we report a vivid example of this, with luminescence conversion from thermally activated delayed fluorescence (TADF) to ultralong room-temperature phosphorescence (URTP) via a facile substituent effect on a rigid benzothiazino phenothiazine tetraoxide (BTPO) core. Pristine BTPO with multiple heteroatoms shows obvious intramolecular charge transfer (ICT) excited states with small exchange energy, featuring TADF. Via delicately functionalizing the BTPO core with peripheral moieties, the excited states of the BTPO derivatives become a hybridized local and charge transfer (HLCT) state in the S1 state and a local excitation (LE) dominated HLCT state in the T1 state, with enlarged energy bandgaps. Upon dispersion in a polymer matrix, the BTPO derivatives exhibit a persistent bright green afterglow with long lifetimes of up to 822 ms and decent quantum yields of up to 11.6%.The decoration of a BTPO core results in a change in the luminescence nature from TADF to URTP. The phosphors in an amorphous PMMA matrix showed monomeric URTP with phosphorescence lifetimes of up to 822 ms and quantum yields of up to 11.6%. 相似文献
43.
本文报道了利用圆二色性(CD)研究了环糊精(CD_x)与o-、m-、p-氯代苯甲酸包结物的包结形态,根据Kajtar扇形规则确定了客体分子在环糊精腔内的位置。 相似文献
44.
在有机电致发光中Tb(Ⅲ)对Eu(Ⅲ)的发光增强现象 总被引:3,自引:0,他引:3
1引言稀土有机配合物,特别是铕和铽的配合物,以其独特的荧光性能在生物免疫荧光分析、痕量元素分析、临床医学等方面有着广泛的应用价值[1].而在近年研究热点之一的有机电致发光研究中,铕和铽的窄带发射特性也吸引了人们的注意,多种配合物被用于这一领域[2].... 相似文献
45.
A series of novel 3′‐(alkyl(hydroxy)amino)‐2′‐fluoronucleoside analogs were prepared via conjugate addition of N‐methylhydroxylamine to various 2‐fluorobutenolides. The adducts 13a and 16 were obtained as single isomers under absolute control of stereochemistry. The crucial N‐demethylation of 23 – 25 was readily achieved by means of DDQ oxidation, followed by nitrone/oxime exchange reaction. By this procedure, a variety of alkyl groups could be efficiently introduced at the 3′‐N‐atom of the nucleoside analogs, some of which might display potentially interesting anti‐HIV properties. 相似文献
46.
Rapid magnetic solid‐phase extraction of Congo Red and Basic Red 2 from aqueous solution by ZIF‐8@CoFe2O4 hybrid composites 下载免费PDF全文
Yan Xu Jingjie Jin Xianliang Li Yide Han Hao Meng Junbiao Wu Xia Zhang 《Journal of separation science》2016,39(18):3647-3654
Core–shell metal–organic framework materials have attracted considerable attention mainly due to their enhanced or new physicochemical properties compared with their single‐component counterparts. In this work, a core–shell heterostructure of CoFe2O4‐Zeolitic Imidazolate Framework‐8 (ZIF‐8@CoFe2O4) is successfully fabricated and used as an solid‐phase extraction adsorbent to efficiently extract Congo Red and Basic Red 2 dyes from contaminated aqueous solution. Vibrating sample magnetometry indicates that the saturated magnetization of ZIF‐8@CoFe2O4 is 3.3 emu/g, which is large enough for magnetic separation. The obtained hybrid magnetic metal‐organic framework based material ZIF‐8@CoFe2O4 can remove the investigated dyes very fast within 1 min of the contact time. The adsorbent ZIF‐8@CoFe2O4 also shows a good reusability. After regeneration, the adsorbent can still exhibit high removal efficiency (~97%) toward Congo Red for five cycles of desorption–adsorption. This work reveals the great potential of core–shell ZIF‐8@CoFe2O4 sorbents for the fast separation and preconcentration of organic pollutants in aqueous solution before high‐performance liquid chromatography analysis. 相似文献
47.
Xiaobin Peng Chao GaoYuying Huang Junbiao PengNaoki Aratani Atsuhiro Osuka 《Tetrahedron letters》2012,53(9):1156-1159
The reactions at the benzylic positions of meso-alkyl-substituted porphyrins have been achieved via the reaction with DDQ in the presence of alcohol or water for the first time, and ethenyl porphyrins from methoxylated porphyrins and an acetoxy porphyrin from the hydroxyl porphyrin were prepared. 相似文献
48.
Derong Cao Qilin Liu Wenjing Zeng Shaohu Han Junbiao Peng Shouping Liu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(8):2395-2405
Two novel alternating copolymers, poly{9,9‐dihexylfluorene‐2,7‐diyl‐alt‐2,5‐dioctyl‐3,6‐bis(4‐phenyl)pyrrolo[3,4‐c] pyrrole‐1,4‐dione} ( P1 ) and poly{9,9‐dihexylfluorene‐2,7‐diyl‐alt‐2,5‐dioctyl‐3,6‐bis(3‐phenyl)pyrrolo[3,4‐c] pyrrole‐1,4‐dione} ( P2 ), derived from 9,9‐dihexylfluorene and diketopyrrolopyrrole (DPP), have been successfully synthesized through palladium‐catalyzed Suzuki polycondensation in good yields. P1 and P2 possess moderate molecular weights and polydispersities, well‐defined structures, and excellent thermal properties with an onset decomposition temperature around 400 °C. Both P1 and P2 in thin films exhibit red photoluminescence from DPP species exclusively, with peaks at 609 and 616 nm, respectively. Cyclic voltammetry studies show that P1 and P2 have low‐lying lowest unoccupied molecular orbital energy levels at ?3.65 eV and reversible reduction processes, so these polymers may constitute another kind of red‐emitting polymer with high electron affinity. Preliminary electroluminescent results of devices with an indium tin oxide/poly(3,4‐ethylenedioxythiophene)/polymer/Ba/Al configuration reveal that P1 may be a promising candidate for red emitters with a maximum brightness of 153 cd/m2 and a maximum external quantum efficiency of 0.13%, whereas the performance of P2 is relatively poor. These differences might originate from different conjugation lengths in their main chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2395–2405, 2006 相似文献
49.
A family of enantiopure azetidine-2-caboxamides was asymmetrically synthesized, and was examined as organocatalyst in direct aldol reactions. A well chosen chiral azetidine-2-caboxamide was found to smoothly catalyze the direct aldol reaction of various benzaldehydes with acetone in brine, and β-hydroxy ketones were produced with enantiomeric excess up to 96%. The reaction of benzaldehydes with cyclic ketones also led to the formation of anti-products in diastereomeric ratio up to 99:1 and enantiomeric excess up to 99%. 相似文献
50.
Ergang Wang Chun Li Junbiao Peng Yong Cao 《Journal of polymer science. Part A, Polymer chemistry》2007,45(21):4941-4949
A novel blue‐emitting polymer based on 3,6‐silafluorene and 2,7‐silafluorene was synthesized via the Suzuki polycondensation. The resulting polymers are readily soluble in common organic solvents, such as toluene, xylene, THF, and chloroform. The thermal, electrochemical, photophysical, and electroluminescence properties of the resulting polymers were investigated. The device fabricated from the copolymer with a configuration of ITO/PEDOT:PSS/PVK/polymer/Ba/Al exhibited an external quantum efficiency of 1.95%, a luminous efficiency of 1.69 cd A?1 and a maximal brightness of 6000 cd m?2. It has been found that the incorporation of the 3,6‐silafluorene unit into the poly(2,7‐silafluorene) main chain can not only improve the color purity of the devices from the resulting copolymer but also enhance its device efficiency. Moreover, no undesired long‐wavelength green emission was observed in the PL spectra of P36‐27SiF90 compared to that of PFO with a dominating emission at 500–600 nm after thermal annealing at 200 °C for 8 h. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4941–4949, 2007 相似文献