A series of 2,3-difunctionalized 5,7-bis(2-thienyl)thieno[3,4-b]pyrazines containing electron-donating and electron-withdrawing side chains are reported to evaluate the potential tuning effect of the side chains on the electronic properties of these common terthienyl building blocks. In order to further study the resulting effects of such side chains in polymeric materials, the dihexyloxy-functionalized terthienyl was copolymerized with fluorene and its electronic properties compared with a number of analogous materials.