1089758-30-4Relevant academic research and scientific papers
Comparative study on the structural, optical, and electrochemical properties of bithiophene-fused benzo[c]phospholes
Matano, Yoshihiro,Miyajima, Tooru,Fukushima, Tatsuya,Kaji, Hironori,Kimura, Yoshifumi,Imahori, Hiroshi
experimental part, p. 8102 - 8115 (2009/09/06)
Three types of bithiophenefused benzo[c]phospholes were successfully prepared by Ti11-mediated cyclization of the corresponding dialkynylated bithiophene derivatives as a key step. Each σ3- phosphorus center of the benzo[c]phosphole subunits was readily transformed into σ4-phosphorus center by Au coordination or oxygenation. In addition, the bithiophene subunit was functionalized at the αα ′-carbon atoms by Pd-catalyzed cross-coupling reactions with heteroarylmetals and by an SNAr reaction with hexafluorobenzene. The experimentally observed results (NMR spectroscopy, X-ray analysis, UV/Vis absorption/fluorescence spectroscopy, and cyclic/differential-pulse voltammetry) have revealed that the structural, optical, and electrochemical properties of the bithiophene-fused benzo[c]phospholes vary considerably depending on the jr-conjugation modes at the bithiophene subunits and the substituents of the heterocyclopentadiene components. The appropriately ring-annulated σ3-P derivatives and σ4P-AuCl complexes were found to emit fluorescence in the orange-red region, and the σ4-P-oxo derivatives proved to undergo reversible one-electron reduction at -1.4 to -1.8V (vs ferrocene/ ferrocenium). These results indicate that the bithiophene-fused benzo[c]phospholes possess narrow HOMOLUMO gaps and low-lying LUMOs, which was confirmed by density functional theory calculations of their model compounds. The time-of-flight measurement of an ITO/benzo[c]phosphole/Al device showed that the electron mobility in the P-oxo derivative is one-order higher than that in AIq3 at low electric fields. The present study demonstrates that the arenefused benzo[c]phosphole skeleton could be a highly promising platform for the construction of a new class of phosphole-based optoelectrochemical materials.
