Synthesis, Self-assembly And Photoelectrical Properties Of Pyrene And Triphenylene-based Discotic Organic Molecules

There are close relationships between performance and structure of the organic photoelectric materials. Among the organic photoelectric materials, organic molecules containing π-conjugated structures have structural diversity and could be easy for modification, different performance requirements could be achieved by changing the molecular design of the structure of main and side chains. Pyrene, triphenylene and their derivatives are two-dimensional structures with typical π-conjugated electron system. By introducing different substituents to the structures, the materials could show well photoelectric properties such as self-assembling properties and nonlinear optical properties, which can be widely used in organic light-emitting diodes, organic solar cells, organic transistors, and organic nonlinear optics.In this paper, a series of pyrene and triphenylene based discotic derivatives were designed and synthesized using various types of coupling reaction and [2+2] click chemistry reactions. Supramolecular self-assembly performance, optical properties and third-order nonlinear optical properties of compounds containing different substituents were characterized to study the effects of different substituents on the properties. The paper includes the following sections:1. A kind of discotic pyrene-based molecule was designed and synthesized using Suzuki coupling reaction. Thiol-containing terminal groups were introduced to the pyrene molecules as modifying groups. By using typical Brust phase-transfer method, gold nanoparticles modified by pyrene-thiol molecule were obtained. Size of the organic composite gold nanoparticles shown in TEM was about 2.5 nm. The aborption band at 532 nm in UV-Vis spectrum proved the presence of gold nanoparticles. By π-π interaction between the gold nanoparticles modified by pyrene compound and small organic disctic pyrene molecule, composite system could co-assembly and a total of assembled structures were observed and fully studied.2. A series of symmetric and asymmetric pyrene derivatives were designed and synthesized by using Sonogashira coupling reactions and no-side effects [2+ 2] click reactions. Different functional groups were introduced into the subsituents of compounds. By UV-Vis absorption spectra and fluorescence emission spectra, the photophysical properties of the products were observed and energy-level structure of the product was characterized by cyclic voltammograms. The results confirmed the introduction of different electron withdrawing groups can well agree with the regulation observed through absorption and electrochemical energy levels of organic molecules. In addition, third-order nonlinear properties of the products were studied by Z-scan technique, and it was found that clear reverse saturable absorption-saturable absorption transitions could be carried out by click reaction modification.3. A series of triphenylene derivatives containing different functional groups were designed and synthesized, mainly through the click reaction to introduce cyano groups to the triphenylene derivatives. By UV-Vis absorption spectra, fluorescence emission spectra, cyclic voltammetry curves and density functional simulation, optical and electrical properties of the compounds were characterized, and it can be proved that different substituents could well affect the shifts of absorption bands and electrochemical energy levels. In addition, third-order nonlinear optical properties of the compounds were studied and it was found that the introduction of different modifying group can effectively change the nonlinear absorption and refraction effects of the product. By solvent exchange method, self-assembly properties of the products were observed and it was found that by modifying the compound through click reactions, regular morphologies were obtained by the cooperation of π-π interaction, steric effects and other interations.