Fluorenylidene-linked triarylamines, potential hole-transporting materials, have been prepared by the palladium-catalyzed Hartwig-Buchwald amination. Their redox and spectral properties were investigated in solution, applying cyclic voltammetry, UV-VIS and EPR spectroscopy, and in situ spectroelectrochemical measurements. N,N,N',N'-Tetraphenylbenzidine (1), N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (2), and triphenylamine (3) served as model substances in the study of the synthesized complex compounds 4 and 5. In structure 4, two triphenylamine centres are linked with a non-conjugated fluorene bridge; in structure 5, two tetraarylbenzidine skeletons with two nitrogens are linked with a conjugated biphenyl-bridge system. In addition, structure 5 contains a non-conjugated fluorene bridge. The presence of the fluorene moiety in the molecular design has a significant influence on the investigated properties of the new materials. In the anodic oxidation of the tetraarylbenzidine-type compounds (1, 2, and 5), two well-defined reversible oxidation peaks were observed. However, the oxidation of the triphenylamine-type structures (3 and 4) is more complex, due to fast consecutive reactions. The dimer-like structures (4 and 5) are characterized by two independent oxidation centres that are simultaneously oxidized at approximately the same potentials. This was confirmed by quantitative cyclovoltammetric as well as UV-VIS investigations.
通过
钯催化的Hartwig-Buchwald胺化反应,制备了荧基亚甲基三芳
胺类化合物,这些化合物具有潜在的空穴传输材料的特性。采用循环伏安法、紫外-可见光谱和电子顺磁共振光谱以及原位光谱电
化学测量,研究了它们在溶液中的氧化还原和光谱性质。在合成的复杂化合物4和5的研究中,N,N,N',N'-四苯基
苯胺(1)、N,N'-二(1-
萘基)-N,N'-二苯基
苯胺(2)和
三苯胺(3)作为模型物质。在结构4中,两个
三苯胺中心通过一个非共轭的荧烯桥连接;在结构5中,两个带有两个氮原子的四苯基
苯胺骨架通过一个共轭的
联苯桥系统连接。此外,结构5含有一个非共轭的荧烯桥。分子设计中荧烯基团的存在对新材料的研究性质有显著影响。在四苯基苯
胺类化合物(1、2和5)的阳极氧化中,观察到两个明确定义的可逆氧化峰。然而,三苯
胺类结构(3和4)的氧化更为复杂,由于快速连续反应。类似二聚体的结构(4和5)具有两个独立的氧化中心,同时在大约相同的电位上被氧化。这得到了定量的循环伏安和紫外-可见光谱研究的证实。