Synthesis Of Asymmetric Organic Semiconductor Materials And S-shaped Double Helicene Based On Thiophene/Selenophene-Based Fused Tricyclic

Dithienothiophene have been widely used in the fields of organic optoelectonic materials and helicenes,due to the good conjugation and multiple intermolecular interactions,such as S-S and S-C.Selenophene is an analogue of thiophene.More and more attention has been paid to selenophene derivatives because of the larger size and more polarizable of selenium atom,and stronger intermolecular Se-Se interaction.In this thesis,using bb-DTT,bb-DST,bb-DSS as building blocks,six kinds of asymmetric organic semiconductors materials and three kinds of thiophene/selenophene-based S-shaped double helicenes have been synthesized.The effects of different atomic radius,polarizability and ?conjugation degree of Se and S atoms on molecular structure and photophysical properties have been studied.The main work can be divided into two parts as followed:1.Synthesis of asymmetric organic semiconductor materials based on thiophene/selenophene-based fused tricyclicUsing 2,5-di(trimethylsilanyl)dithieno-[2,3-b:3?,2?-d]thiophene((TMS)2-bb-DTT),2,5-di(trimethylsilanyl)diseleno-[2,3-b:3?,2?-d]thiophene((TMS)2-bb-DST) and 2,5-di(trimethylsilanyl)diseleno-[2,3-b:3?,2?-d]selenophene((TMS)2-bb-DSS)as building blocks via NBS bromination,Suzuki coupling reaction,deprotection TMS,DMF formylation and Wittig reaction,six kinds of asymmetric organic semiconductors materials namely,1(40%),2(43%),3(23%),4(26%),5(33%)and6(34%)have been synthesized.All intermediates and target compounds have been characterized by NMR,IR,MS,HRMS.Compounds 1-6 are all cis and trans isomers(cis : trans = 1 : 3).The UV-vis absorption spectra of 1,3,5 and 2,4,6 are generally similar in shape and exhibit two major absorption bands within230-275 nm(Band-I)and 300-350 nm(Band-II).The progressive red-shifts in absorption spectra have been found with the increase of selenium atoms in Band I(230-275 nm).The slight blue-shifts in absorption spectra have been found with the increase of selenium atoms in Band II(300-350 nm).The results of absorption spectrum and cyclic voltammetry of compounds 2,4,6 show that the optical band gap decreases and the HOMO levels increase gradually with the increase of the number of selenium atoms.2.Synthesis of S-shaped double helicene based on thiophene/selenophene-based fused tricyclicStarting from(TMS)2-bb-DTT,(TMS)2-bb-DST and(TMS)2-bb-DSS,through NBS bromination,DMF formylation,Wittig reaction,and photocyclization,three kinds of S-shaped double helicenes,namely,rac-7(23%),rac-8(11%)and rac-9(18%)have been synthesized.All intermediates and target compounds have been characterized by 1H NMR,13 C NMR,IR,MS,HRMS.Compounds rac-7,rac-8,and rac-9 are all composed of one [5]helicene and one [6]helicene.X-ray single crystal diffraction analysis of rac-7 and rac-8 shows the structure of S-type double spiroene,directly.Compounds rac-7 and rac-8 all belong to the triclinic space group P-1.Hetero[5]helicene in rac-7to rac-8 the inner helix becomes smaller(rac-7: 0.93 ?,rac-8: 0.88 ?),but turns in-plane becomes larger(rac-7: 231 o,rac-8: 232o).However,hetero[6]helicene in rac-7 to rac-8 the inner helix and turns in-plane all become larger(rac-7: 2.51 ?,rac-8: 2.52 ?,rac-7: 278 o,rac-8: 283o).With the introduction of selenium atom,the S···S interaction transform into Se···S and Se···Se interaction.UV-vis absorption and fluorescence spectra behaviors of rac-7,rac-8,and rac-9 were studied.The progressive red-shifts in absorption spectra were found with the increase of selenium atoms,and the optical band gaps estimated from the absorption edges gradually narrowed down from rac-7 to rac-9.The fluorescence intensity and fluorescence quantum yield decreased obviously.