Abstract
We designed and synthesized unsubstituted 4,4′-bibenzo[c]thiophene 4,4′-BBT and its silyl-substituted derivatives 1,1′-Si-4,4′-BBT and 1,1′,3,3′-Si-4,4′-BBT with one or two tert-butyldimethylsilyl groups on each thiophene ring, as new π-building blocks in emitters, photosensitizers and semiconductors for organic optoelectronic devices. The characterization of 4,4′-BBT, 1,1′-Si-4,4′-BBT and 1,1′,3,3′-Si-4,4′-BBT was successfully determined by FTIR, 1H and 13C NMR measurements, high-resolution mass spectrometry (HRMS) analysis, photoabsorption and fluorescence spectroscopy, cyclic voltammetry (CV) and density functional theory (DFT) calculations. Moreover, a single-crystal X-ray structural analysis was successfully made for 1,1′-Si-4,4′-BBT and 1,1′,3,3′-Si-4,4′-BBT. The photoabsorption and fluorescence maxima (λabsmax and λflmax) of the three 4,4′-bibenzo[c]thiophene derivatives in toluene exhibit bathochromic shifts in the order of 4,4′-BBT (359 nm and 410 nm) < 1,1′-Si-4,4′-BBT (366 nm and 420 nm) < 1,1′,3,3′-Si-4,4′-BBT (371 nm and 451 nm). The HOMO and LUMO energy levels rise in the order of 4,4′-BBT (−5.55 eV and −2.39 eV) < 1,1′-Si-4,4′-BBT (−5.45 eV and −2.34 eV) < 1,1′,3,3′-Si-4,4′-BBT (−5.34 eV and −2.30 eV), but the rise of the HOMO energy level is larger than that of the LUMO energy level, resulting in the bathochromic shift of the photoabsorption band from 4,4′-BBT to 1,1′,3,3′-Si-4,4′-BBT. The fluorescence quantum yields (Φfl) of 4,4′-BBT, 1,1′-Si-4,4′-BBT and 1,1′,3,3′-Si-4,4′-BBT in toluene are 0.41, 0.41 and 0.36, respectively. It is worth mentioning that in the solid state 1,1′-Si-4,4′-BBT and 1,1′,3,3′-Si-4,4′-BBT show relatively high Φfl-solid values of 0.22 and 0.25, respectively, whereas 4,4′-BBT exhibits poor solid-state fluorescence properties (Φfl-solid < 0.02). This work provides an efficient synthetic method for the 4,4′-bibenzo[c]thiophene derivatives and their photophysical properties in the solution and solid state, electrochemical properties and X-ray crystal structures.
Highlights
The characterization of BBT-1, BBT-2 and BBT-3 was successfully determined by FTIR, 1H and 13C NMR measurements, highresolution mass spectrometry (HRMS) analysis, photoabsorption and uorescence spectroscopy, cyclic voltammetry (CV) and density functional theory (DFT) calculations
We demonstrated that BBT-2 with a tert-butyldimethylsilyl group on each thiophene ring was obtained by the reaction of 1 with tetramethylethylenediamine (TMEDA) and nBuLi, followed by treatment with tert-butyldimethylsilyl chloride (TBDMSCl)
We have achieved a facile synthesis of 4,40-bibenzo[c]thiophene derivatives, unsubstituted 4,40-bibenzo[c]thiophene 4,40-BBT and its silyl-substituted derivatives 1,10-Si-4,40-BBT and 1,10,3,30Si-4,40-BBT with one or two tert-butyldimethylsilyl groups on each thiophene ring, and revealed their photophysical properties in the solution and in the solid state and electrochemical properties
Summary
Benzo[b]thiophene as a p-building block has created considerable scienti c interest in synthetic organic chemistry, photochemistry, electrochemistry and theoretical chemistry as well as materials chemistry, because it is an especially crucial player for functional materials due to the air-stability and commercial availability (Fig. 1). benzo[b]thiophene derivatives are key constituents of emitters, semiconductors and photosensitizers for organic optoelectronic devices, such as organic lightemitting diodes (OLEDs), organic eld-effect transistors (OFETs), organic photovoltaics (OPVs) and dye-sensitized solar cells (DSSCs). much effort has been made towards the construction and characterization of fused benzo[b]thiophene systems such as thienoacenes (e.g., [1]benzothieno[3,2-b] [1]benzothiophene (BTBT), dinaphtho[2,3-b:20,30-f]thieno[3,2-b] thiophene (DNTT) and dianthra[2,3-b:20,30-f]thieno[3,2-b]thiophene (DATT))6a and thiophene-fused naphtho[2,3-b:6,7-b] dithiophene diimide (NDTI)6b in the past two decades. Much effort has been made towards the construction and characterization of fused benzo[b]thiophene systems such as thienoacenes (e.g., [1]benzothieno[3,2-b] [1]benzothiophene (BTBT), dinaphtho[2,3-b:20,30-f]thieno[3,2-b] thiophene (DNTT) and dianthra[2,3-b:20,30-f]thieno[3,2-b]thiophene (DATT))6a and thiophene-fused naphtho[2,3-b:6,7-b] dithiophene diimide (NDTI)6b in the past two decades. These benzo[b]thiophene derivatives have been used as organic semiconductors with high carrier mobility and stability under ambient conditions. The benzo[c]thiophene unit contains a thiophene ring in the structure. PITN has a low band gap (Eg 1⁄4 1.0–1.2 eV), which is about 1.0 eV lower than that of polythiophene (PT), because the polymer backbone of PITN intrinsically stabilizes its quinoidal state, 18870 | RSC Adv., 2021, 11, 18870–18880
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have