Syntheses of Diverse Donor-Substituted Bisbenzofuro[2,3-b:3’,2’- e]pyridines (BBZFPys) via Pd Catalysis, and Their Photophysical Properties
Yuhei Itai, Yuji Nishii, Patrycja Stachelek, Przemyslaw Data, Youhei Takeda, Satoshi Minakata, Masahiro Miura
The Journal of Organic Chemistry
A series of bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys) bearing a chlorine functionality have been efficiently synthesized through a Pd-catalyzed double oxidative intramolecular C–H/C–H coupling of mono-chlorinated 2,6-diaryloxypyridines. The subsequent Buchwald-Hartwig amination of the chlorinated BBZFPys allowed for the access to a new class of donor-acceptor (D-A) π-conjugated compounds that comprise of BBZFPy as an electron-acceptor (A) and diarylamines as a donor (D) units. The investigation of the steady-state photophysical properties of the prepared D-A compounds revealed that they are emissive in both of solution and solid states in blue-to-green color region. The singlet-triplet energy splitting (DEST) was found much smaller than that of substituent- free BBZFPy (0.70 eV), ranging from 0.01 to 0.56 eV. The time-resolved spectroscopy revealed that the D-A compounds comprising of a bis(tert-butyl)carbazole as the D and CF3-attached BBZFPy as the A showed delayed fluorescence (DF) in a non-polar matrix host material (Zeonex®), while in a polar matrix (DPEPO), room-temperature phosphorescence (RTP) was faintly observed. Furthermore, organic light-emitting diodes (OLEDs) fabricated with the D-A compounds as a blue-emitter showed a moderate external quantum efficiencies (EQEs) up to 1.5%.
Fluorescence, Photoluminescence, Quantum yield, Optical properties, Phosphorescence, Solid state, Organic chemistry, Materials