Synthesis And Properties Of Dendrimers Containing Triphenylamine Dendrons

The organic optoelectronic functional materials and devices have attracted great interest by academia and industry as a result of their huge potential applications. Many organic molecular devices have been studied in detail, such as organic light-emitting diode, organic filed effect transistor, organic photovoltaic cell and organic laser. The partial properties of these devices have been up or over those of the inorganic semiconductor devices. In fact, the huge development of science and technology is depended on the excellent properties of molecular material, and the properties of molecular materials are crucial to the performance of the photoactive and electroactive devices. Therefore, it is most interest to design and synthesize novel organic semiconductor materials with excellent properties.Triphenylamine (TPA) derivatives have been widely investigated for almost two decades because these compounds have showed excellent thermal and electrochemical stability, electron donating ability, and optoelectronic properties. Considerable effort in synthetic chemistry, in particular by Shirota and co-workers, has led to the development of many classes of TPA-based compounds as hole-transporting or electroluminescent materials. To our knowledge, most of triphenylamine derivatives are connected by the N-C single-bond and obtained either through palladium-catalyzed cross-coupling reactions requiring expensive and extremely air-sensitive palladium catalysts or through copper-catalyzed Ullmann condensations usually involving high temperatures and prolonged reaction time, but few papers about triphenylamine derivatives connected by the C-C double bond were published.1. We have synthesized two new conjugated dendrimers bearing triphenylamine moiety as dendrons and 1, 3, 5 triphenylbenzene as a core through a simple Wittig-Horner reaction. The emission peak of TPB-TPA9 was red shifted 34nm from that of TPB-TPA3, which showed that there was obviousπ-π* delocalization with the increase of the generation of dendrimers. The absorption maxima of TPB-TPA3 and TPB-TPA9 in films, for example, were red-shifted by 3nm and 1nm, respectively, or in other words, the higher the generation, the smaller the red-shift in the absorption. The glass-transition temperatures (Tg) of the dendrimers increased from 115 to 165°C with the increase of the generation of dendrimers because the multibranched molecules with higher generation tend to hinder translational, rotational, and vibrational motions of the molecule and result in Tg enhancement.2. We have synthesized two new conjugated dendrimers bearing triphenylamine moiety as dendrons and truxene as a core through Heck reaction, because truxene exhibited more powerful hole-transporting ability than 1, 3, 5-triphenylbenzene. The emission peak of Tr-TPA9 is red shifted 31nm from that of Tr-TPA3, which shows that there is obviousπ-π* delocalization with the increase of the generation of dendrimers. The absorption maxima of Tr-TPA3 and Tr-TPA9 in films are red-shifted by 4nm and 1nm, and hence the dendrimers films are in a good amorphous state. We found that Tg of Tr-TPA3 and Tr-TPA9 are 115OC and 140OC, respectively. It shows that Tg is enhanced with increasing generation of dendrimers.3. We have synthesized three conjugated dendrimers bearing triphenylamine moiety as dendrons and anthracene as core, which possess AIE properties.Comparably, we have synthesized three conjugated dendrimers bearing triphenylamine moiety as dendrons and benzene as core, which possess ACQ properties. We found that Tg of An-TPA6 and An-TPA14 are 160OC and 220OC, respectively.4. We have synthesized DSA and its derivatives. We found the most important feature in the crystal is that an anthracene group interacts with two hydrogen atoms of the neighboring molecule to form two CH…πhydrogen bonds, and then a network is formed in the crystal .These supramolecular interactions induced close stacking, and extremely strong fluorescence emission in the solid state. We are currently investigating the electroluminescent properties of these dendrimers.