Bithiophenes

The syntheses, structures, properties, and reactions of the three bithiophenes (10-12), and their derivatives, were the subject of an excellent comprehensive review published in 1992 and covering the literature up 

94JOC442, 94TL1977], which, unless structurally constrained to planarity, are generally nonplanar. 

---

Thiophene, 2,2-bithiophene, and 2,2, 5, 2"-terthiophene derivatives from Chinese medicinal plants as oncogene signal transduction inhibitors (proteinki-nase C inhibitors) 99PAC1101. 

Figure 2. Cyclic voltammograms of a poly(2,2 -bithiophene)-coated electrode in acetonitrile containing 0.1 M Bu4NC 04.34 (Reprinted from G. Zotti, C. Schiavon, and S. Zecchin, Irreversible processes in the electrochemical reduction of polythiophenes. Chemical modifications of the polymer and charge-trapping phenomena, Synth. Met. 72 (3) 275-281, 1995, with kind permission from Elsevier Sciences S.A.)...

An improved synthesis of dithieno[3,2-A2, 3 -<7]thiophene 15a has been achieved from 2,3-dibromothiophene 304 (Scheme 57). Lithiation of 2,3-dibromothiophene 304 using -butyllithium followed by oxidative coupling with cupric chloride provided 3,3 -dibromo-2,2 -bithiophene 305 in 79% yield. Treatment of 305 with 2 equiv of -butyllithium in ether at —78 °C under nitrogen for 40 min and then adding benzenesulfonic acid thioanhydride and leaving the reaction mixture to reach room temperature afforded dithieno[3,2-A2, 3 -<7]thiophene 15a in 70% yield <2002TL1553>. 

Dipolar cycloaddition of 2,4-(trimethylsilyl)- and 2,4-(trimethylgermyl)-substituted thiophene-1,1-dioxides as well as silylated 2,2 -bithiophene-1,1-dioxides was investigated. It was shown that only the C(4)=C(5) double bond of 2,4-disubstituted thiophene-1,1-dioxides interacts with acetonitrile oxide to give thienoisoxazoline dioxides. Bithiophene derivatives were inactive or their reaction with nitrile oxide was accompanied by desilylation. Cycloaddition of benzonitrile oxide with all mentioned sulfones did not occur. The molecular structure of 3a-methyl-5.6a-bis(trimethylgermyl)-3a,6a-dihydrothieno 2.3-c/ isoxazole 4,4-dioxide was established by X-ray diffraction (263). ... 

M. Zagorska and B. Krische, Chemical synthesis and characterization of soluble poly(4,4 -dialkyl-2,2 -bithiophenes), Polymer, 31 1379-1383, 1990. 

M. Berggren, G. Gustafsson, O. Inganas, M.R. Andersson, T. Hjertberg, and O. Wennerstrom, White light from an electroluminescent diode made from poly[3(4-octylphenyl)- 2,2 -bithiophene] and an oxadiazole derivative, Appl. Phys. Lett., 76 7530-7534, 1994. 

Bis(dimesitylboryl)-2,2 -bithiophene (BMB-2T, 242) forms a stable amorphous glass and emits pure blue color with a high fluorescence QE of 86% in THF solution [270]. However, an OLED with ITO/m-MTDATA/TPD/BMB-2T/Mg Ag emits with a broad emission due to an exciplex with TPD. The exciplex can be prevented by insertion of a thin layer of 1,3,5-tris(biphenyl-4-yl)benzene (TBB) between TPD and BMB-2T, leading to a pure blue emission. It seems that the boron complex or boron-containing compounds easily form an exciplex with common HTMs. Other similar blue emitter materials also demonstrate such behavior. 

T. Noda, H. Ogawa, and Y. Shirota, A blue-emitting organic electroluminescent device using a novel emitting amorphous molecular material, 5,5 -/)/.v(dimcsityIboryl)-2,2 -bithiophene, Adv. Mater., 11 283-285 (1999). 

FIGURE 5.4 Chemical structures of photo- and electroluminescent polymers employed for polarized LEDs poly(2-methoxy-5-(2 -ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) poly[2,5-dioctyloxy-l, 4-diethynyl-phenylene-a/t-2,5,-bis(2 -ethylhexyloxy)-l,4-phenylene] (EHO-OPPE) poly(p-phenylene), PPP poly(3-(4-octylphenyl)-2,2 -bithiophene), PTOPT poly(p-phenylene vinylene), PPV poly(3-alkylthio-phene vinylene), P3AT Acetoxy-PPY PPV-polyester, poly(9,9-dialkyl fluorene), PF. 

Fig. 4 Thermally evaporated (a) 0.75, 1.27, and 1.31 monolayers of 5,5 -bis(4-hexylphenyl)-2,2 -bithiophene [6PTTP6], which were incorporated in FETs and (b) show a dramatic increase in mobility at 1.31 monolayers, (c) The partial second layer is illustrated schematically to bridge voids in the underlying monolayer, providing pathways for increased charge transport...

Huang J, Sun J, Katz HE (2008) Monolayer-dimensional 5,5 -bis(4-hexylphenyl)-2,2 -bithiophene transistors and chemically responsive heterostructures. Adv Mater 20 2567-2572... 

---