Aza[6]Helicene And Thiaze[6]Helicene:Synthesis,Characterization And Properties

Due to extended ?-conjugation structure,fused heterocyclic aromatic compounds have potential applications in the field of organic electronics.Helicenes are polycyclic aromatic compounds consisting of ortho-fused benzene or other aromatic rings.A helicene with a rigid backbone generally possesses a good fluorescent property and a high decomposition temperature.Helical and nonplanar geometry not only generates the blockage of the degree of ?-conjugation and reduction of molecular aggregations,but also facilitates amorphous structure in solid state.These characteristics make the helicene a good candidate for optoelectronic materials.The main content of this dissertation contains two parts:1.Successful synthesis of two novel fused heterocyclic aromatic compounds by photochemical reactions,that is,15-hexyl-15H-tetraphenyl[1,2-e]indole and 14-hexyl-14H-benzo[4',5']thieno[2',3':7,8]naphtha[1,2-e]indole;2.Structural characterizations,property measure-ments and quantum calculations were also carried out.15-hexyl-15H-tetraphenyl[1,2-e]indole based on units of indole and anthracene was synthesized successfully.Indole-5-carboxaldehyde and 2-bromoanthracene as initial reactants were utilized to produce the aza[6]helicene by four steps,that is,alkylation substitution reaction,Witting reaction,Heck reaction and photocyclization.1H NMR,13C NMR,HRMS,MALDI-TOF were used to verify the compound,and the thermal properties,electrochemical properties as well as optical properties were also studied.The maximum absorption peaks and maximum emission peaks in solvents such as hexane,dichloromethane,ethyl acetate,trichloromethane,acetonitrile and methanol were found to range from 299 to 303 nm and 415 to 457 nm,respectively.The maximum emission peak in film-state underwent bathochromic shift and were found at 467 nm.The fluorescence quantum yield of the compound in trichloromethane was measured to be as high as 21%.By the electrochemical measurement,HOMO and LUMO energy levels,and the band gap of the compound were calculated to be-5.20 eV and-2.34 eV,and 2.86 eV,respectively.TGA and DSC curves showed that the decomposition temperature of the compound was 246.57 ?,indicating the good thermal stability.Theoretical calculations showed the maximum absorption peak was mainly attributed to the HOMO?LUMO+1 transition.14-hexyl-14H-benzo[4',5']thieno[2',3':7,8]naphtha[1,2-e]indole was first prepared as a thiaze[6]helicene based on indole.Indole-5-carboxaldehyde and 2-bromodibenzothiophene as starting reactants were used to synthesize the target compound through four steps:alkylation substitution reaction,Witting reaction,Heck reaction and photocyclization.1H NMR,13C NMR,HRMS were investigated,and the thermal properties,electrochemical properties as well as optical properties were also studied.The maximum absorption peaks and emission peaks in solvents such as hexane,toluene,dichloromethane,tetrahydrofuran,ethyl acetate,trichloromethane,and methanol were measured to range from 298 to 311 nm and 397 to 403 nm,respectively.The PL peak in the film-state was located at 424 nm.The fluorescence quantum yield of the compound in dichloromethane was measured to be as high as 32%.Through the electrochemical measurement,HOMO,LUMO energy levels and the band gap of the compound were calculated to be-5.04 eV,-2.03 eV,and 3.01 eV,respectively.TGA and DSC curves demonstrated the decomposition temperature of 388.44 ? were much higher than that of the first compound.The maximum absorption peak was mainly attributed to the HOMO-1?LUMO+1 transition by the theoretical calculations.