Oligothiophenes trimer

On the basis of these considerations, Hotta and Waragai [174] have studied absorption spectroscopy of the thin solid films of alkyl-substituted oligothiophenes (trimer to hexamer see Figure 8.14 for chemical structures) over near-UV to mid-IR regions. They have studied the absorption spectra of these materials which were taken in both neutral and doped states. The most outstanding feature that distinguishes the solid-state spectra from those taken in solution is that the former display a strong n-n absorption band in the oxidized... 

Oligothiophenes have been selected as the target molecule, since their photoexcitation processes are well established and they are known as electron donors with large extinction coefficients of the Tj state and radical cation in the D0 state [105-108], The S0 and Tj states of the trimer, tetramer, and... 

Figure 8.5 Comparison between the B3LYP/6-31 G(d,p) theoretical infrared spectra of (a) diprotonated a,a -bis(aminomethyl)terthiophene, (b) unprotonated trimer and (c) experimental infrared spectrum of a,a -bis(aminomethyl)terthiophene in neutral form. Experimental spectrum obtained on powdered samples in pressed KBr pellets. Reprinted with permission from V. Hernandez, H. Muguruma, S. Hotta, J. Casado and ). T. Lopez Navarrete, A combined spectroscopic and theoretical study of a series of aminomethyl end-capped oligothiophenes with potential applications in thin film devices, J. Phys. Chem. A, 104, 735-740 (2000), Copyright 2000 American Chemical Society...

Figure 8.14. Chemical structures of a series of the dimethyl-substituted oligothiophenes. The structures denote dimethyl-bithiophene (dimer DMBT), dimethylterthiophene (trimer DMTT), dimethylquaterthiophene (tetramer DMQtT), di-methylquinquethiophene (pentamer DMQqT), and dimethyl-sexithiophene (hexamer DMSxT) from the top. The x and y axes represent the directions of the molecular long and short axes, respectively. Reprinted with permission from Reference 174. Copyright 1993 American Chemical Society.

The species with the lower oxidation state characterized by the two sharply resolved subgap absorptions are observed for the oligothiophenes of trimer and compounds with a higher degree of polymerization. 

Silylsubstituted oligothiophenes have also been prepared to investigate the effect of dn Pn conjugation with the terminal silicon atom. The a-a and a,co silylated dimer, trimer and tetramer (Scheme 14.8) were directly prepared via lithiation of the parent bi, ter and quaterthiophene [20]. 

From the capped trimer 331 and tetramer 332 Miller et al. prepared the first protonated oligothiophenes 348 and 349 in solution by the treatment with tri-fluoroacetic acid (TFA) [Eq. (91)] [252]. Since a protonated species could not be obtained from Me-Ts-Me 262, the methoxy groups clearly enhance the... 

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