Synthesis of thiophene/phenylene co‐oligomers. V. Functionalization at molecular terminals toward optoelectronic device applications

We report the synthesis of various thiophene/phenylene co‐oligomers with a total number of thiophene and benzene (phenylene) rings of 5 and 6 with various terminal groups. Those terminal groups have been chosen from among alkyl groups, methoxy groups, trifluoromethyl groups, and cyano groups. The molecular backbone of these compounds comprises phenyl‐ or biphenylyl‐capped thiophene (or oligothiophene) or an alternating co‐oligomer. The synthesis is based on either the Suzuki coupling reaction or the Negishi coupling reaction. These reaction schemes enabled us to obtain the target compounds in high quality. In particular, the latter coupling method turned out to produce the compounds at a high yield. The terminal groups are expected to produce various functionalities based upon their electron donating character (alkyl groups and methoxy groups) or electron withdrawing character (trifluoromethyl groups and cyano groups). Additionally some of these groups bring about enhanced solubility. This will lead to the production of a diversity of modified compounds of thiophene/phenylene co‐oligomers. To give an example that demonstrates usefulness of the target compounds, we present optoelectronic data that are associated with their device applications.