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521.
Mingchun Guo Dr. Qiangqiang Meng Dr. Wenyao Chen Prof. Dr. Zheng Meng Dr. Ming-Liang Gao Prof. Dr. Qunxiang Li Prof. Dr. Xuezhi Duan Prof. Dr. Hai-Long Jiang 《Angewandte Chemie (International ed. in English)》2023,62(26):e202305212
The chemical microenvironment modulation of metal nanoparticles (NPs) holds promise for tackling the long-lasting challenge of the trade-off effect between activity and selectivity in catalysis. Herein, ultrafine PdCu2 NPs incorporated into covalent organic frameworks (COFs) with diverse groups on their pore walls have been fabricated for the semihydrogenation of alkynes. The Cu species, as the primary microenvironment of Pd active sites, greatly improves the selectivity. The functional groups as the secondary microenvironment around PdCu2 NPs effectively regulate the activity, in which PdCu2 NPs encapsulated in the COF bearing −CH3 groups exhibit the highest activity with >99 % conversion and 97 % selectivity. Both experimental and calculation results suggest that the functional group affects the electron-donating ability of the COFs, which successively impacts the charge transfer between COFs and Pd sites, giving rise to a modulated Pd electronic state and excellent catalytic performance. 相似文献
522.
Dr. Suresh Moorthy Dr. Hugues Lambert Dr. Neetha Mohan Thomas Schwarzlose Prof. Werner M. Nau Dr. Elina Kalenius Dr. Tung-Chun Lee 《Angewandte Chemie (International ed. in English)》2023,62(32):e202303491
In the gas phase, thermal activation of supramolecular assemblies such as host–guest complexes leads commonly to noncovalent dissociation into the individual components. Chemical reactions, for example of encapsulated guest molecules, are only found in exceptional cases. As observed by mass spectrometry, when 1-amino-methyl-2,3-diazabicyclo[2.2.2]oct-2-ene (DBOA) is complexed by the macrocycle β-cyclodextrin, its protonated complex undergoes collision-induced dissociation into its components, the conventional reaction pathway. Inside the macrocyclic cavity of cucurbit[7]uril (CB7), a competitive chemical reaction of monoprotonated DBOA takes place upon thermal activation, namely a stepwise homolytic covalent bond cleavage with the elimination of N2, while the doubly protonated CB7⋅DBOA complex undergoes an inner-phase elimination of ethylene, a concerted, electrocyclic ring-opening reaction. These chemical reaction pathways stand in contrast to the gas-phase chemistry of uncomplexed monoprotonated DBOA, for which an elimination of NH3 predominates upon collision-induced activation, as a heterolytic bond cleavage reaction. The combined results, which can be rationalized in terms of organic-chemical reaction mechanisms and density-function theoretical calculations, demonstrate that chemical reactions in the gas phase can be steered chemoselectively through noncovalent interactions. 相似文献
523.
Ritapa Chaudhuri Thumpati Prasanth Dr. Jyotirmayee Dash 《Angewandte Chemie (International ed. in English)》2023,62(7):e202219003
Herein, we demonstrate for the first time that noncanonical DNA can direct macrocyclization-like challenging reactions to synthesize gene modulators. The planar G-quartets present in DNA G-quadruplexes (G4s) provide a size complementary reaction platform for the bio-orthogonal macrocyclization of bifunctional azide and alkyne fragments over oligo- and polymerization. G4s immobilized on gold-coated magnetic nanoparticles have been used as target templates to enable easy identification of a selective peptidomimetic macrocycle. Structurally similar macrocycles have been synthesized to understand their functional role in the modulation of gene function. The innate fluorescence of the in situ formed macrocycle has been utilized to monitor its cellular localization using a G4 antibody and its in cell formation from the corresponding azide and alkyne fragments. The successful execution of in situ macrocyclization in vitro and in cells would open up a new dimension for target-directed therapeutic applications. 相似文献
524.
Haipei Zhao Xuehao Xiu Dr. Mingqiang Li Prof. Shaobo Dai Mingyang Gou Leyang Tao Prof. Xiaolei Zuo Prof. Chunhai Fan Prof. Zhongqun Tian Prof. Ping Song 《Angewandte Chemie (International ed. in English)》2023,62(14):e202214450
Dynamic interactions of enzymes, including programmable configuration and cycling of enzymes, play important roles in the regulation of cellular metabolism. Here, we constructed a super DNA-enzymes molecule (SDEM) that comprises at least two cascade enzymes and multiple linked DNA strands to control and detect metabolism. We found that the programmable SDEM, which comprises glucose oxidase (GOx) and horseradish peroxidase (HRP), has a 20-fold lower detection limit and a 1.6-fold higher reaction rate than free enzymes. An SDEM can be assembled and disassembled using a hairpin structure and a displacement DNA strand to complete multiple cycles. An entropically driven catalytic assembly (catassembly) enables different SDEMs to switch from an SDEM with GOx and HRP cascades to an SDEM with sarcosine oxidase (SOX) and HRP cascades in over six orders of magnitude less time than without the catassembly to detect different metabolisms (GO and sarcosine) on demand. 相似文献
525.
526.
Xiuxing Liu Dr. Qiuyan Liao Dr. Jie Yang Prof. Zhen Li Prof. Qianqian Li 《Angewandte Chemie (International ed. in English)》2023,62(24):e202302792
Phosphorescence of organic materials is highly dependent on intermolecular interactions, for the sensitive triplet excitons toward environment and aggregated structures. However, until now, relationship between phosphorescence and intermolecular interactions is still unclear for complicated influence factors and uncontrollable aggregated behaviors. Herein, taking temperature as the controlled variable, the afterglow can continuously change from blue to green, then to yellow, even achieve the white emission with deuteration process. It is mainly due to the hierarchical architectures of molecular aggregates with rational distribution of intermolecular interactions, as well as gradually unlocking process of interactions with different energies. Accordingly, the one-to-one correspondence between the determinate interactions and excited triplet states have been established, guiding accurate design of desirable phosphorescence materials by hierarchical control of aggregated structures. 相似文献