Effect of molecular geometry and extended conjugation on the performance of hydrogen-bonded semiconductors in organic thin-film field-effect transistors

A general synthetic method has been used for the condensation of the 7-azaindole substructure at both extremes of centrosymmetric fused polyheteroaromatic systems. Four different aromatic spacers (benzene, naphthalene, anthracene and pyrene) that modify the molecular geometry and the pi-conjugated surface have proved the ability of 7-azaindole to work as a building block that can control the crystal packing through reciprocal hydrogen bond interactions. Two possible self-assembled columnar arrangements have been observed as a result of the pi-pi interactions between hydrogen-bonded ribbon-like supramolecular structures. A detailed comparative analysis of the molecular organisation driven by hydrogen bonding and pi-stacking, in combination with DFT calculations, has revealed an interesting evolution of the charge transport parameters. Organic thin-film field-effect transistors have been fabricated with the hydrogen-bonded semiconductors, reaching mobilities that demonstrate the potential of this supramolecular approach to control the molecular organisation and promote the electronic communication between the organic building blocks.