New synthetic methods have been developed for the preparation of 4-alkyl- and 4-aryl-pyrrolo[2,3-d:5,4-d']bisthiazole (PBTz) building blocks from 2,4-thiazolidinedione. The resulting PBTz products have been fully characterized via structural, electronic, and optical methods, thus allowing full comparison to the previously reported dithieno[3,2-b:2',3'-d]pyrrole (DTP) analogues. Such comparisons then allow a detailed discussion of the relative electronic effects of the various methods utilized to tune the properties of the parent DTP building block.