Synthesis and characterization of structurally defined head-to-tail coupled oligo(3-alkylthiophenes)
A very efficient and selective synthesis to regioregular HT-coupled oligo(3-alkylthiophenes) has been developed. A series of benzyl ester-capped oligothiophenes up to the decamer has been synthesized using successive iodination/Suzuki-coupling reaction sequences. For the corresponding hexamer it was shown that saponification and decarboxylation to the HT-coupled oligo(3-alkylthiophene) proceeds in high yields. The dependence of the electronic properties on the chain length of the conjugated oligomers was investigated. The oligomers form very stable and well-ordered adsorbates at the solid–liquid interface and these were imaged by scanning tunneling techniques.