5- Hexyl-2,2 -bithiophene

The absorption spectra of the monodendrons and dendrimers of all three generations are quite similar all of them are slightly broadened and red shifted with respect to the model 5-hexyl-2,2 -bithiophene due to the influence of the silicon atom to a n system of the bithiophenes. It is noteworthy that attachment of the methylsilyl group to 5-hexyl-2,2 -bithio-phene leads to an increase of the molar extinction coefficient (s) from 13,000 to 19,000 NT1 cm-1. 

As discussed in Sect. 2.1, luminescence efficiency of bi- and terthiophenes can be increased by silylene- and disilylelene substituents. This effect might be enhanced by a further branching of the chromophore to avoid aggregation. Ponomarenko and his group reported a significant increase of the luminescence quantum yield Op in dilute solutions of a series of mono-, di-, tri-, and tetra(5 -hexyl-2,2 -bithiophene)silanes from 0.06 to 0.20 while the absorption and luminescence spectra... 

Side-chain substitution Small molecule organic semiconductors can also be rendered solution processable by attachment of flexible side chains. The substitution pattern needs to be designed carefully so that the side chains, which are needed to impart adequate solubility and film forming properties, do nof inferfere with the ability of the molecule to Jt-stack. Katz reported side-chain-substituted small molecule semiconductors such as dihexylanthradithiophene [47,48] that can be solution-deposited with mobilities of 0.01-0.02 cmWs. In bis(hexyl-bithiophene)benzene solution-cast onto a heated Si02 substrate, mobilities of up to 0.03 cmWs were reported [49]. Due to the relatively low solubility of these molecules, growth... 

The conformational analysis of oligothiophenes by use of a combined molecular dynamics (MD)/NMR spectroscopic protocol has been carried out. A series of MD simulations were performed for 2-(2-thienyl)-3-hexylthiophene 173, 2,5-bis(3 -hexyl-2 -thienyl)thiophene 176, and 2,5-bis(4 -hexyl-2 -thienyl)-thiophene 177, with a new MM2 torsional parameter set developed earlier for unsubstituted and methyl-substituted 2,2 -bithiophene. 

Figure 7.15a is a schematic illustration of the field-effect transistor sensor with semiconductor 5, 5 -bis (4-n-hexyl-phenyl)-2, 2/-bithiophene (6PTTP6) film serving as the active layer. This unfunctionalized sensor shows some inherent sensitivity to DMMP. Figure 7.16 compares the change of the saturation source-drain current of 6PTTP6 sensor before and after exposure to saturated DMMP vapor, with source-drain voltage Vb set to be —100 V. 

G. Zotti, G. Schiavon, S. Zecchin, A. Berlin, A. Canavesi and G. Pagani, Self-assembly and electropolymerization of pyrrole-and bithiophene-n-hexyl-ferrocene molecules on ITO electrodes, Synth. Met., 84, 239-240 (1997). 

H60PT 5,5 -bis(4-hydroxyhexyloxyphenyl)-2,2" bithiophene, 6PTTP6 5,5 -bis(4-n-hexyl-phenyl)-2,2" bithiophene, PEDOT poly(3,4-ethylenedioxythiophene), PSS poly(styrenesulfonate)... 

However, electrochemically polymerized 3-alkyl-2,2 -bithiophenes (alkyl = hexyl, dodecyl) give conducting films whose electrical conductivities are independent of the length of the alkyl chains [485-487],... 

Scheme 54 Oxidation of 2,5 -bis(n-hexyl)-2,2 -bithiophene with m-CPBA [61]...

In the oxidation of dimethyl-bis-(5-trimethylsilyl-2-thienyl)silane, having two thiophene moieties, with one equivalent of m-CPBA, one thiophene ring was preferentially oxidized to afford only the mono-sulfone 52 in 36% yield. After further addition of m-CPBA, the corresponding mono-sulfone 52 and bis-sulfone 53 were obtained in 21 and 41% yields, respectively (Scheme 53) [64], In another example, the oxidation of 2,5 -bis(n-hexyl)-2,2 -bithiophene was found to be difficult the monodioxide 54 was obtained in low yield (10%), but no bis-6,6-dioxide was observed (Scheme 54) [61],... 

The impact of alkyl side chain substituents on conjugated pol5uners on the photovoltaic properties of bulk heterojimction solar cells has been studied extensively (128). However, their impact on small molecules has not received adequate attention. In order to assess the effect of side chains, a series of star-shaped molecules based on a triphenylamine core, bithiophene, and dicyanovinyl units deriva-tized with various alkyl end-capping groups of methyl, ethyl, hexyl and dodecyl have been S5mthesized. These molecules were studied to get structure-property relationships. 

Ethyl-2,2 -bithiophene 3-Hexyl-2,2 -bithiophene 3-Dodecyl-2,2 -bithiophene 148 89 295 1.75 170... 

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