Donor‐substituted oligothiophenes, 1 synthesis and properties of a series of methylthio oligothiophenes

A homologous series of donor‐substituted oligothiophenes 7–9 bearing methylthio groups in the „outer”︁ β‐positions were synthesized up to a quaterthiophene. The physical properties are dependent on the chain length of the conjugated system. The compounds exhibit biological activities. Due to the substitution pattern, even the longer oligomers exhibit good film‐forming properties and could be electropolymerized to the corresponding donor‐substituted polythiophenes P7–P9 with a stereoregular structure. The electronic properties were found to be dominated by the donor strength of the substituents.