Conjugated Molecules Of Two Dimensional Polycyclic Aromatic Hydrocarbons Benzothiadiazole Based:Design,Synthesis And Applications

In recent years, with the research of polycyclic aromatic hydrocarbons, organic photovoltaic materials have developed rapidly. It is well known that extend the π conjugation system can improve the performance of the molecular device for PAHs material. With the increasing of π conjugated degree, the stability is becoming worse and worse, the current solution is to increase highly electronegative atom and strong electron withdrawing groups for acene system, so that can reduce HOMO energy level to improve the stability of the molecule, so as to improve the device performance. In order to obtain aromatic hydrocarbons(PAHs) materials with superior performance, we use 5,6-dibromobenzo-[2,1,3]thiadiazole as the core unit, and obtain the following results:(1) At first, we determined 5,6-dibromobenzo-[2,1,3]thiadiazole as the core unit, then because of 5,6-dibromobenzo-[2,1,3]thiadiazole two bromine adjacent, so we have chosen the way of alkyne cyclization to expand two-dimensional conjugate system. In order to ensure the solubility of the material, and more efficient charge transfer, we choose the alkyl thiophenes and double alkyl phenyl as substituent, via C-H activation, Suzuki coupling, Sonogashira coupling and some other methods constructed two acetylenic coupling intermediate 4a and 4b. In two platinum chloride under the action we got acetylenic substituents and one side constitute the six membered ring products 5a, 5b. After that we use a classical scholl reaction to prepare 6a and 6b, But there are some outgrowth exist. And 4a, 4b in Pd Cl2 catalysis and on both sides of the substituents are formed by the structure of the five ring that is 8a and 8b, and significant isomerization was observed. Finally, through the method of fluorenone confirmed the acetylenic coupling with both substituents generated bilateral five membered ring. This work makes us on characteristics of alkyne cyclization have in-depth understanding, to lay the foundation for the future development of π system using the method.(2) We use Stille coupling reaction and scholl reaction as the main means of synthesized 16 a and 16 b, two helicene highly twisted conjugated molecules, whose dihedral angle reached 44.8 degrees. 16 a and 16 b have the same structure, the only difference lies in the alkyl chain, 16 b selected branched-C10, solubility than 16 a, and two materials by chloroform solution spin coating method of prepared field effect transistor devices differ greatly, 16 b measured hole mobility as 3.27 × 10-2cm2 V-1 s-1, 16 a measuring hole mobility was 1.95 × 10-4 cm2 V-1 s-1. It is proved that the alkyl chain can not only affect the solubility, but also can change the accumulation mode.(3) We designed and synthesized a series linear transistor material based on benzo thiadiazole, which has the advantages of simple structure, short synthesis route, but has very good transistor performance, which measured the FTC8(7b) hole mobilities reach 0.177 cm2 V-1 s-1, on-off ratio was 8.32 × 105. The hole mobility of compound TFTC12(7a) was measured at 0.070 cm2 V-1 s-1, and the switch ratio was 2.92 × 104. Such a simple structure to obtain such performance, cost-effective. And the HOMO of TFTC12(7a), FTC8(7b) were-6.13 e V and-5.85 e V, because of they exist as the form of fluorenone, also the stability is very good.