"Genetically modified" spider-like oligothiophenes : electron properties and polymerization ability

Multithiophene-based semiconductors are a well-known, popular class of organic semiconductors of very promising potential applications in a wide variety of fields, like electronics, energetics, sensoristics. Starting from our previous exhaustive work on “spider-like” branched oligothiophenes, affording a detailed and reliable rationalization of the relationships between structure and electronic properties1,2, many structure modifications have been recently developed with respect to the original all-thiophene systems, aiming to achieve finer and wider modulation of both the HOMO and LUMO levels. In particular, the “core” of our oligothiophene systems has been modified by choosing appropriate building blocks of different electron-richness, asymmetrically affecting both the LUMO and HOMO energy levels and localization along the main conjugated backbone, thus achieving one more freedom degree in tuning the electron properties of the molecule. Our voltammetric investigation has been performed on a wide series of “genetically-modified” spider-like oligothiophenes, exploring both the effect of core modification at constant thiophene side chains, and the effect of increasing length and/or branching in the thiophene side chains at constant modified core. The core modification appears to be much more effective on the HOMO and LUMO energy levels and positions, while effective conjugation in the thiophene side chains is more determining on the oligomerization ability. The exhaustiveness of our investigation affords interpretative and predictive criteria which could usefully exploited in target-oriented molecular design.