Comparison between SiMe2 and CMe2 Spacers as σ-Bridges for Photoinduced Charge Transfer
摘要:
The potential of dimethylsilylene and isopropylidene sigma-spacers as bridges for photoinduced charge transfer (CT) in 4-cyano-4'-(dimethylamino)- and 4-cyano-4'-methoxy-substituted diphenyldimethylsilanes and 2,2-diphenylpropanes was studied. Fluorescence solvatochromism and time-resolved microwave conductivity measurements show that upon photoexcitation a charge separated state (D(.+)sigma A(.-))* is populated in all compounds. Excited state dipole moments for a given donor-acceptor combination are, irrespective of the bridge, equal. The CT states of the silanes are however lying at lower energies, implying that the presence of silicon thermodynamically facilitates the CT process. Cyclic voltammetry data of model compounds show that this is a consequence of the lowering of the acceptor reduction potential by the silicon bridge. It was however inferred from radiative decay rates that the electronic coupling between the CT and locally excited states as well as the coupling between the ground and CT state is larger for the carbon-bridged compounds. As shown by both solution and solid state electronic spectra and radiative decay rates, the photophysics of the D sigma A compounds are dominated by intensity borrowing of the CT transitions from transitions localized in the D sigma and sigma A chromophores.
B(C
<sub>6</sub>
F
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<sub>3</sub>
‐Catalyzed Tandem Friedel‐Crafts and C−H/C−O Coupling Reactions of Dialkylanilines
作者:Gaowen Zhai、Xueting Liu、Wentao Ma、Guoqiang Wang、Liu Yang、Shuhua Li、Youting Wu、Xingbang Hu
DOI:10.1002/asia.202000763
日期:2020.10
Tandem Friedel‐Crafts (FC) and C−H/C−O coupling reactions catalyzed by tris(pentafluorophenyl) borane (B(C6F5)3) were achieved without using any other additive in the absence of solvent. This process can be used for the reactions between a series of dialkylanilines and vinyl ethers with good isolated yields of bis(4‐dialkylaminophenyl) compounds. Based on combined theoretical and experimental studies
在没有溶剂的情况下,无需使用任何其他添加剂,即可实现三(五氟苯基)硼烷(B(C 6 F 5)3)催化的串联弗里德-克来福特(FC)和CH-H / C-O偶联反应。该方法可用于一系列二烷基苯胺和乙烯基醚之间的反应,分离出的双(4-二烷基氨基苯基)化合物收率良好。在理论和实验研究相结合的基础上,提出了可能的反应机理。B(C 6 F 5)3可以分别激活FC和CH / C-O偶联反应的C = C和C-O键。FC反应是缓慢的,其后是快速的CH / CH耦合。
Zur Kenntnis der Reaktionsfähigkeit der polarisierten einfachen Bindung
作者:R. Wizinger、R. Gross
DOI:10.1002/hlca.19520350153
日期:1952.2.1
Bei der Einwirkung von Jod auf 2,2-Bis-[4-dimethylaminophenyl]-propan entsteht Bis-[4-dimethylaminophenyl]-methyl-carbenium-trijodid, während eine Methylgruppe als Jodmethyl abgespalten wird. Die theoretische Bedeutung dieser Reaktion wird aufgewiesen.