Chemical oligothiophenes

The chemical scheme of oligothiophenes (wT, where rt stands for the number of thiophene units) is shown in Figure 14-14. 

Figure 14-14. Chemical structure of unsubstituted (R = H) and end-substituted oligothiophene.

Polythiophenes (including oligothiophenes) are one of the most studied and important classes of linear conjugated polymers [444,445], Versatile synthetic approaches to PTs (chemical [446] and electrochemical [447]), easy functionalization and unique, widely tunable electronic properties have been the source of tremendous interest in this class of polymers. 

Thus, the combined experimental and theoretical results indicate that the chemical shift observed for the S(2p) core level, of about 1.6 eV, should be due to a secondary effect from the attachment of Al atoms to the adjacent carbon atoms. Indeed, this is fully consistent with ab initio Hartree-Fock ASCF calculations of the chemical shifts in aliuninum-oligothiophene complexes [87]. From calculations on a Al2/a-3T complex, where the two Al atoms are attached to the a-carbons on the central thiophene unit, the chemical shift of the S(2p) level for the central sulfur atom is found to be 1.65 eV, which is in close agreement with the experimental value of about 1.6 eV [84]. It should be pointed out that although several different Al-thiophene complexes were tested in the ASCF calculations, no stable structure, where an Al atom binds directly to a S atom, was found [87]. 

There are several ways to modify the molecular structure of oligothiophenes via chemical... 

FIGURE 5.3.1 Chemical structure of alkyl-substituted oligothiophenes. 

FIGURE 5.3.3 Chemical structures of an oligothiophene with internal double bonds and asymmetric oligothiophene derivatives. 

Other applications such as use as a chemical sensor, are in principle possible, but not considered so far. This is not surprising because, in general, chemically active materials are not suitable for electronic applications unless the devices are encapsulated. Although oxygen dopes oligothiophenes, this reaction is slow and in particular the reverse step after evacuation leads to an extremely slow response of the conductivity which... 

Figure 3.6 Electrochemical detection of thrombin by interaction between nncleic acid and a redox-active oligothiophene polyelectrolyte (4). (A) Blocking the electrical contact between the polyelectrolyte and the electrode by means of a aptamer-thrombin complex. (B) Separation of the aptamer-thrombin complex by the formation of a PNA-opened aptamer dnplex on the electrode and its analysis by the redox-active polyelectrolyte. (C) Voltammetric response to the analysis of different concentrations of thrombin according to method B (a) OM (b) 125nM (c) 250nM (d) 500nM, 1 p,M (f) 2 p,M. (Reprinted with permission from Floch et al., 2006. Copyright 2006 American Chemical Society.)...

Figure 119. Synthesis of one-dimensional porphyrin-oligothiophene polymers. Reprinted with permission from Segawa, H. Kunimoto, K. Susumu, K. Taniguchi, M, Shimidzu, T. /. Am. Chem. Soc. 1994, 116, 11193. 1994 American Chemical Society.

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