Crystal structure and optical properties of n-pyrrole end-capped thiophene/phenyl co-oligomer: Strong h-type excitonic coupling and emission self-waveguiding

In view of their exploitation in working devices, mainly for their emission properties, the interest in crystals of thiophene/phenylene co-oligomers has recently increased. Here, we describe the strategies for the organic synthesis and crystal growth of a novel oligothiophene-based co-oligomer (thiophene/phenyl co-oligomer end-capped with pyrrole) designed to explore the effect of an electron-rich aromatic ring, such as pyrrole, to end-cap oligothiophenes. The growth by the melted material is also discussed and suggested for implementation in real devices. The UV-visible optical characterization is provided, and the results (absorption and emission excitonic transitions, H-type aggregation, self-waveguiding of the emitted light) are interpreted on the basis of the crystallographic data in the regime of strong intermolecular coupling.