Synthesis And Spectroscopic Behavior Of The Derivatives Of Dithieno [2,3-b:4’,3’-d] Silole

The^-conjugated compounds with dithienosiloles unit as building block have low reduction potential and low-lying lowest unoccupied molecular orbital (LUMO) energy level. The unique electronic structure make dithienosilole-based compounds can be used as functional materials in organic field effect transistor (OFETs), organic light-emitting diodes (OLEDs) and dye-sensitized solar cells (DSSCs). So the π-conjugated compounds with dithienosilole unit as building block have attracted more and more attention. As far as we known, there are three symmetrical isomers, dithieno[3,2-b:2’,3’-d]silole, dithieno[2,3-b:3’,2’-d]silole and dithieno[3,4-b:4’,3’-d]silole have been reported. In this thesis, we found a novel synthetic route to dithieno[2,3-b:4’,3’-d]siloles, and we synthesize functional materials whcih used dithieno[2,3-b:4’,3’-d]silole as a building block. My research work is separated into four parts as following:1. After Br/Li exchange in4,4’-dibromo-2,2’,5,5’-tetrakis(trimethylsilyl)[3,3’]bithienyl (3) with4.4equiv/-BuLi in diethyl ether at-78℃for1h and45℃for14h, and then the reaction mixture was quenched with water at45℃,7,7-dimethyl-4,6-di(trimethylsilyl)-dithieno[2,3-b:4’,3’-d]silole (1) was generated in93.2%isolated yield. On the contrary, after Br/Li exchange at-78℃for1h, and-50℃for1h, we could obtain7,7-dimethyl-2,4,6-tri(trimethylsilyl)-dithieno[2,3-b:4’,3’-d]silole only in93.0%isolated yield.1and2were confirmed by1H NMR,13C NMR, HRMS, FTIR and X-ray. We also proposed possible mechanism for the formation of1and2through deuterated reaction and mono-Br/Li exchange reaction.2. Mono-, di-, and tribrominated dithieno[2,3-b:4’,3’-d]siloles were prepared by1or2under different equiv of NBS in pretty good yields. The bromination positions were confirmed by1H NMR,13C NMR, HRMS, FTIR and X-ray. Upon the treatment with NBS under controlled conditions, dithieno[2,3-b:4’,3’-d]silole can be selectively brominated on the three α-positions to produce mono-, di-, and tribrominated dithieno[2,3-b:4’,3’-d]siloles. The order of activity positions of bromination on dithieno[2,3-b:4’,3’-d]silole could be confirmed as position4> position2> position6in our work.3.1,2-di(7,7-dimethyl-6-trimethylsilyl-dithieno[2,3-b:4’,3’-d]silole)-4-ehene(12) could be prepared in two steps with1.1)7,7-dimethyl-6-trimethylsilyl-4-formyldithieno[2,3-b:4’,3’-d]silole(11,85.2%) was prepared by Vilsmeier reaction.2) The McMurry reaction was employed in making12in97.7%.1,2-di{7,7-dimethyl-4,6-di(trimethylsilyl)-dithieno[2,3-b:4’,3’-d]silole}-2-ehene(14) could be prepared in two steps.1)1was treated with LDA and quenching with DMF to give7,7-dimethyl-4,6-di(trimethylsilyl)-2-formyldithieno[2,3-b:4’,3’-d]silole (13) in85.3%yield.2) The McMurry reaction was employed in making14in97.0%. In the crystal,12and14are planar molecule. The study on thermal stability indicated that12and14had good thermal stability.After Br/Li exchange in6, and then the reaction mixture was quenched with DMC,1,2-di(7,7-dimethyl-6-trimethylsilyl-dithieno[2,3-b:4’,3’-d]silole-4)-methanone (15) was generated in78.2%yield. The McMurry reaction was employed in making1,1,2,2-tetra(7,7-dimethyl-6-trimethylsilyl-dithieno[2,3-b:4’,3’-d]silole-4)-ethane(16,71.6%) which was an abnormal McMurry coupling result. And we also proposed possible mechanism for this abnormal McMurry coupling reaction.The photophysical properties of12,14and16were investigated by UV/Vis spectroscopy and fluorescence spectroscopy. Absorption peak of12or14had a obviously red shift than7.12,14and16had high conjugation which was due to the introduction of double bond. They also had strong fluorescence in solution or in solid state which was benefit for OLED.4. With11and13as starting material, bromination reaction, Stille reaction and Knoevenagel reacion getting7,7-dimethyl-2-N,N-bis(phenylamino)phenyl-6-trimethylsilyl-dithieno[2,3-b:4’,3’-d]silole-2-cyanoacrylic acid (ZJC-1,85.3%) and7,7-dimethyl-4,6-di{N,N-bis(phenylamino) phenyl}-dithieno[2,3-b:4’,3’-d]silole-2-cyanoacrylic acid (ZJC-2,85.2%). Dithieno[2,3-b:4’,3’-d] silole unit was a binary π-conjugated spacer between triphenylamine electron donor and a hydrophilic cyanoacrylic acid electron acceptor. ZJC-1was the typical structure of D-π-A, ZJC-2was the structure of2D-π-A.