Thiophene, oligo

Figure 2. Solution phase synthesis of the oligo(thiophene ethynylene)s by the divergent/convergent doubling approach.

The band occurring at about 345 nm could be assigned to absorptions involving the spider legs, as suggested by the extinction coefficient values s which are linearly dependent on the number of bithienyl pendants present in the molecule (2, 4, and 6). The extinction coefficient is known to be dependent upon the number of the thiophene units also in linear a-oligo thiophenes. 

Reactions that include the dimerization of two radical cations are, for example, those of anethole [313], pyrroles [314], oligopyrroles [315], thiophenes [316], oligo-thiophenes [317], diphenylamine [318], triphenylamine [319], WWdimethylaniline [320], and diphenylpolyene [321]. 

The conducting and physical properties can be modified by the use of 3-/4-substituents, or A-substituents in the case of pyrrole. The counter-ions can be incorporated into a side-chain (self-doping), as in the polymer of 3-(thien-3-yl)propanesulfonic acid. Oligo(thiophenes) are also useful in these applications and have been specifically synthesised up to 27 units long by palladium(0)-catalysed couplings or via the diacetylene synthesis (17.12.1.1). ... 

Oligo(thiophenes) are also useful in these applications and have been specifically synthesised up to 27 units long by palladium(0)-catalysed couplings or via the diacetylene synthesis (section 14.13.2.2). ... 

K. Sakamoto, Y. Takashima, H. Yamaguchi, A. Harada, Preparation and properties of rotaxanes formed by dimethyl-/3-cyclodextrin and oligo(thiophene)s with /3-cyclodextrin stoppers, J. Org. Chem., 2007, 72, 459 65. 

Figure II.6.8 shows the data obtained from the UV/Vis spectroelectrochemical study of a oligo-thiophene (see structure in Fig. II.6.8) in a LIGA cell [73]. The oligo-thiophene was dissolved in a solution of 0.1 M NBU4PF6 in acetonitrile and voltammograms were recorded at two different temperatures, at (A) h-20°C and (B) —40°C. What appears to be an electrochemically reversible oxidation process at +1.16 V can be seen to become much more complicated at lower temperature. The analysis of spectroelectrochemical data clearly indicates the presence of two distinct products of which one, the radical cation A ", is detected at ambient temperature (Fig. II.6.8 A). A second product, the dimer is present at 20°C in low concentration. However, upon reducing the temperature in the spectroelectrochemical cell to —40°C, the dimer becomes the dominant product (Fig. II.6.8B) causing a change in both the voltammetric and the UV/Vis spectroelectrochemical response.

Fig. II. 6.8 UV/ s spectroelectrochemical detection of the oxidation products for the oxidation of an oligo-thiophene in acetonitrile (0.1 M NBuaPFe). The voltammetric tind in situ spectroelec-trochemictil measurements were conducted at (A) 20 C and (B) —40°C in a LIGA cell system...

The first series of oligothiophenes functionalized with 12-crown-4 (2.174 n = 0, 1) and 18-crown-6 (2.175) via flexible alkoxy spacers were reported by Bauerle etal. (Chart 1.37) [270, 271]. The oligomers were synthesized in 66, 48 and 72% yield, respectively, by reaction of co-brominated alkyl(oligo)thiophenes and 12-crown-4-methanol or 18-crown-6-methanol using tetrabutylammonium... 

N. Camaioni, G. Ridolfl, V. Fattori, L. Favaretto and G. Barbarella, Oligo thiophene-5, -dioxides as a class of electron-acceptor materials for organic photovoltaics, Appl. Phys. Lett., 84, 1901-1903 (2004). 

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