193978-23-3Relevant articles and documents
Control Interlayer Stacking and Chemical Stability of Two-Dimensional Covalent Organic Frameworks via Steric Tuning
Wu, Xiaowei,Han, Xing,Liu, Yuhao,Liu, Yan,Cui, Yong
, p. 16124 - 16133 (2018)
Layer stacking and chemical stability are crucial for two-dimensional covalent organic frameworks (2D COFs), but are yet challenging to gain control. In this work, we demonstrate synthetic control of both the layer stacking and chemical stability of 2D COFs by managing interlayer steric hindrance via a multivariate (MTV) approach. By co-condensation of triamines with and without alkyl substituents (ethyl and isopropyl) and a di- or trialdehyde, a family of two-, three-, and four-component 2D COFs with AA, AB, or ABC stacking is prepared. The alkyl groups are periodically appended on the channel walls and their contents, which can be synthetically tuned by the MTV strategy, control the stacking model and chemical stability of 2D COFs by maximizing the total crystal stacking energy and protecting hydrolytically susceptible backbones through kinetic blocking. Specifically, the COFs with higher concentration of alkyl substituents adopt AB or ABC stacking, while lower amount of functionalities leads to the AA stacking. The COFs bearing high concentration of isopropyl groups represent the first identified COFs that can retain crystallinity and porosity in boiling 20 M NaOH solution. After postsynthetic metalation with an iridium complex, the 2,2′-bipyridyl-derived COFs can heterogeneously catalyze C-H borylation of arenes, whereas the COF with isopropyl groups exhibits much higher activity than the COFs with ethyl groups and nonsubstituents due to the increased porosity and chemical stability. This work underscores the opportunity in using steric hindrance to tune and control layer stacking, chemical stability and properties of 2D COFs.
Azo compounds with different sized fluorophores and characterization of their photophysical properties based on trans to cis conformational change
Ingale, Gajanan,Seo, Young Jun
, p. 5247 - 5250 (2014)
We synthesized fluorophores of different sizes attached to azo derivatives, such as thiophene-, naphthalene-, anthracene-, and pyrene-based azo compounds, and studied their photophysical properties. The compounds exhibited strong color and intensity changes in absorption and emission during the structural change from trans to cis, which also resulted in a large Stokes shift and a difference in quantum yield. Depending on their size, the compounds had different rates of transformation from the trans to cis structure: less conjugated (smaller) fluorophore azo compounds showed higher transition rates than more conjugated (larger) ones.
Recyclable Pd2dba3/XPhos/PEG-2000 System for Efficient Borylation of Aryl Chlorides: Practical Access to Aryl Boronates
Cai, Mingzhong,Luo, Chengkai,Xu, Caifeng,Huang, Bin
, p. 1339 - 1346 (2021/12/02)
Pd2dba3/XPhos in poly(ethylene glycol) (PEG-2000) is shown to be a highly stable and efficient catalyst for the borylation of aryl chlorides with bis(pinacolato)diboron. The borylation reaction proceeds smoothly at 110 °C, delivering a wide variety of aryl boronates in good to excellent yields with high functional group tolerance. The crude products were easily isolated via simple extraction of the reaction mixture with cyclohexane. Moreover, both expensive Pd2dba3 and XPhos in PEG-2000 system could be readily recycled and reused more than six times without loss of catalytic efficiency.
Benzoic Acid-Promoted C2-H Borylation of Indoles with Pinacolborane
Zou, Youliang,Zhang, Binfeng,Wang, Li,Zhang, Hua
supporting information, p. 2821 - 2825 (2021/04/13)
A benzoic acid-promoted C2-H borylation of indoles with pinacolborane to afford C2-borylated indoles is developed. Preliminary mechanistic studies indicate BH3-related borane species formed via the decomposition of pinacolborane to be the probable catalyst. This transformation provides a prompt route toward the synthesis of diverse C2-functionalized indoles.
