Obayashi Kotaro, Imato Keiichi, Aoyama Satoshi, Enoki Toshiaki, Akiyama Seiji, Ishida Mio, Suga Seiji, Mitsudo Koichi, Ooyama Yousuke
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University 1-4-1 Kagamiyama Higashi-Hiroshima 739-8527 Japan
Science & Innovation Center, Mitsubishi Chemical Corporation 1000, Kamoshida-cho, Aoba-ku, Yokohama-shi Kanagawa 227-8502 Japan.
RSC Adv. 2021 May 25;11(31):18870-18880. doi: 10.1039/d1ra01189h. eCollection 2021 May 24.
We designed and synthesized unsubstituted 4,4'-bibenzo[]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 -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, H and C 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 ( and ) of the three 4,4'-bibenzo[]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 ( ) 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 values of 0.22 and 0.25, respectively, whereas 4,4'-BBT exhibits poor solid-state fluorescence properties ( < 0.02). This work provides an efficient synthetic method for the 4,4'-bibenzo[]thiophene derivatives and their photophysical properties in the solution and solid state, electrochemical properties and X-ray crystal structures.
我们设计并合成了未取代的4,4'-联苯并[]噻吩（4,4'-BBT）及其硅烷基取代衍生物1,1'-Si-4,4'-BBT和1,1',3,3'-Si-4,4'-BBT，每个噻吩环上带有一个或两个丁基二甲基硅烷基，作为用于有机光电器件的发光体、光敏剂和半导体中的新型π-构建块。通过傅里叶变换红外光谱（FTIR）、氢核磁共振（H NMR）和碳核磁共振（C NMR）测量、高分辨率质谱（HRMS）分析、光吸收和荧光光谱、循环伏安法（CV）以及密度泛函理论（DFT）计算，成功确定了4,4'-BBT、1,1'-Si-4,4'-BBT和1,1',3,3'-Si-4,4'-BBT的特性。此外，还成功对1,1'-Si-4,4'-BBT和1,1',3,3'-Si-4,4'-BBT进行了单晶X射线结构分析。三种4,4'-联苯并[]噻吩衍生物在甲苯中的光吸收和荧光最大值（λabs和λem）呈现红移，顺序为4,4'-BBT（359 nm和410 nm）＜1,1'-Si-4,4'-BBT（366 nm和420 nm）＜1,1',3,3'-Si-4,4'-BBT（371 nm和451 nm）。最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）能级的升高顺序为4,4'-BBT（-5.55 eV和-2.39 eV）＜1,1'-Si-4,4'-BBT（-5.45 eV和-2.34 eV）＜1,1',3,3'-Si-4,4'-BBT（-5.34 eV和-2.30 eV），但HOMO能级的升高幅度大于LUMO能级，导致光吸收带从4,4'-BBT到1,1',3,3'-Si-4,4'-BBT发生红移。4,4'-BBT、1,1'-Si-4,4'-BBT和1,1',3,3'-Si-4,4'-BBT在甲苯中的荧光量子产率（ΦF）分别为0.41、0.41和0.36。值得一提的是，在固态下，1,1'-Si-4,4'-BBT和1,1',3,3'-Si-4,4'-BBT分别显示出相对较高的ΦF值，为0.22和0.25，而4,4'-BBT的固态荧光特性较差（ΦF＜0.02）。这项工作为4,4'-联苯并[]噻吩衍生物提供了一种有效的合成方法，并研究了它们在溶液和固态中的光物理性质、电化学性质以及X射线晶体结构。
