摘要/Abstract

在本工作中，发展了一种新的合成策略，利用薁各位点的反应活性差异选择性地在薁的1-位进行官能团化，合成了由苯环（B）或噻吩并[3，2-b]噻吩基团（TT）桥联的二薁二酰亚胺化合物AzAzBDI-1、AzAzBDI-2和AzAzTTDI.AzAzBDI-2的单晶结构显示其具有扭曲的共轭骨架，相邻的两个分子通过分子间薁的七元环和五元环的π-π相互作用形成二聚体，二聚体与二聚体之间通过强的π-π相互作用形成滑移的一维堆积.用紫外-可见光吸收光谱和循环伏安法对三个化合物的光谱和电化学性质进行表征，计算出各分子的轨道能级和带隙.基于三个化合物的有机场效应晶体管器件（OFET）均表现出n-型主导的双极性有机半导体特性.其中AzAzTTDI表现出最优的OFET性能，其电子和空穴迁移率分别为0.087 cm²·V^－1·s^－1和8.8×10^－3 cm²·V^－1·s^－1.
关键词: 薁, 非苯芳烃, 酰亚胺, 有机场效应晶体管, 有机半导体
Azulene, a bicyclic nonbenzenoid aromatic hydrocarbon, shows completely different physicochemical properties compared with its isomeric naphthalene. Herein, we made use of the diverse reactivity of each position on azulene to design a new synthetic strategy for azulene-based diimides bridged by phenyl or thieno[3,2-b]thiophenyl group, 2-(azulen-2'-yl)-5-(azulen-2''-yl)benzene-1,1':4,1''-tetracarboxylic diimides (AzAzBDI-1/2) and 2-(azulen-2'-yl)-5- (azulen-2''-yl)thieno[3,2-b]thiophene-3,1':6,1''-tetracarboxylic diimide (AzAzTTDI). The key step was double trifluoroacetylation at 1-position of two azulene moieties of the molecule followed by hydrolysis, anhydridization and imidization to obtain the target compounds. The single crystal structure analysis demonstrates that AzAzBDI-2 has twisted molecular backbone. The adjacent two molecules form a dimer through the intermolecular π-π stacking (0.365 nm) between the five-membered ring and the seven-membered ring of two different azulene units. Strong π-π intermolecular interactions (0.355 nm) exist among the dimers to form a slipped one-dimensional (1D) packing motif in the crystal. For three compounds, the optoelectronic properties were investigated by UV-vis absorption spectra and cyclic voltammetry, and their energy levels of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) and the energy gaps were calculated. The HOMO/LUMO energy levels of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI are －5.56/－3.28 eV, －5.56/ －3.30 eV and －5.57/－3.42 eV, respectively. The end absorptions of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI in thin films show obvious red-shift (13, 13 and 25 nm) relative to those in CHCl₃ solution, indicating strong intermolecular interactions in solid state. The charge carrier transport properties of three compounds were studied through organic field-effect transistors (OFETs). Bottom-gate and top-contact OFET devices of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI were fabricated by spin-coated their respective solution on octadecyltrimethoxysilane (OTMS)-treated SiO₂/Si substrates. Under nitrogen atmosphere, all of these three compounds displayed electron-dominated ambipolar organic semiconductor characteristics. The
electron mobilities of AzAzBDI-1 and AzAzBDI-2 were 0.068 cm²·V^－1·s^－1 and 0.086 cm²·V^－1·s^－1 and the hole mobility were 3.1×10^－4 cm²·V^－1·s^－1 and 1.5×10^－3 cm²·V^－1·s^－1, respectively. OFETs based on AzAzTTDI showed the highest electron mobility and hole mobilities of 0.087 cm²·V^－1·s^－1 and 8.8×10^－3 cm²·V^－1·s^－1, respectively. The X-ray diffraction (XRD) and atomic force microscopy (AFM) studies demonstrate thin films of AzAzBDI-1, AzAzBDI-2 and AzAzTTDI show better crystallinity and form larger size of microstructures by annealing, which is consistent with the enhanced device performance after thermal annealing.
Key words: azulene, nonbenzenoid aromatic hydrocarbon, imides, organic field-effect transistors, organic semiconductor


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