Positively charged phosphorus‐containing heterocycles are characteristic core skeletons for functional molecules. While various phosphonium‐containing five‐ or six‐membered ring compounds have been reported, seven‐membered ring phosphepinium has not yet been fully studied. In this study, dithieno[2,3‐b;3,2‐f]phosphepinium ions containing electron‐donating aminophenyl groups were synthesized. An X‐ray crystallographic analysis of the resulting donor‐acceptor‐donor dyes revealed a bent conformation of the central seven‐membered ring. This compound exhibited fluorescence in the near‐infrared region with a bathochromic shift of 70 nm compared to phosphepine oxide congener and a large Stokes shift. High fluorescence quantum yields were obtained even in polar solvents due to the suppression of the nonradiative decay process. The theoretical study revealed that the phosphepinium skeleton is highly electron‐accepting owing to the orbital interaction between a px orbital of the phosphonium moiety and a π* orbital of the 1,3,5‐hexatriene moiety. Owing to the lower‐lying px orbital in the phosphonium moiety compared with that of the phosphine oxide and the bent conformation of the seven‐membered ring, the phosphepinium ring effectively furnishes a px‐π* conjugation. A large structural relaxation with the contribution of a quinoidal resonance structure is suggested in the excited state, which is responsible for the intense emission with a large Stokes shift.
Thiophene-Fused Borepins As Directly Functionalizable Boron-Containing π-Electron Systems
作者:David R. Levine、Maxime A. Siegler、John D. Tovar
DOI:10.1021/ja502644e
日期:2014.5.14
preparation of two isomeric dithienoborepins (DTBs), boron-containing polycyclic aromatics featuring the fusion of borepin and thiophene rings. DTBs exhibit reversible cathodic electrochemistry and boron-centered Lewis acidity in addition to enhanced electronic delocalization relative to benzo-fused analogues. Boron's precise position within the conjugation pathway of DTBs significantly affected electronic
Isomeric Dithienophosphepines: The Impact of Ring Fusion on Electronic and Structural Properties
作者:Kevin Padberg、Johannes D. R. Ascherl、Frank Hampel、Milan Kivala
DOI:10.1002/chem.201905429
日期:2020.3.18
The synthesis and extensive experimental (X-ray crystallography, UV/Vis spectroscopy, cyclic voltammetry) and theoretical (DFT calculations) characterization of two isomeric dithieno[b,f]phosphepines (DTPs) are presented herein. The relative orientation of the phosphepine and the thiophene moieties has a decisive impact on the electronic and structural properties of these compounds. Moreover, the thiophene