F. Di Maria, M. Zangoli, M. Gazzano, E. Fabiano, D. Gentili, A. Zanelli, A. Fermi, G. Bergamini, D. Bonifazi, A. Perinot, M. Caironi, R. Mazzaro, V. Morandi, G. Gigli, A. Liscio, G. Barbarella
Adv. Funct. Mater., 2018, 28 (32), 1801946.
Oligothiophenes are π-conjugated semiconducting and fluorescent molecules whose self-assembly properties are widely investigated for application in organic electronics, op-toelectronics, biophotonics and sensing. We report here an approach to the preparation of crystal-line oligothiophene nano/micro-fibers based on the use of a ‘sulfur overrich’ quaterthiophene building block, -T4S4-, containing in its covalent network all the information needed to promote the directional, π-π stacking driven, self-assembly of Y-T4S4-Y oligomers into fibers with hier-archical supramolecular arrangement from nano- to microscale. We show that when Y varies from unsubstituted thiophene to thiophene substituted with electron withdrawing groups, a wide redistribution of the molecular electronic charge takes place without substantially affecting the aggregation modalities of the oligomer. In this way a structurally comparable series of fibers is obtained having progressively varying optical properties, redox potentials, photoconductivity and type of prevailing charge carriers (from p- to n-type). A thorough characterization of the fibers based on SEM, CD, CV, X-ray diffraction, UV-vis and PL spectroscopies, photoconductivity and KPFM measurements is reported. With the aid of DFT calculations, combined with powder X-ray diffraction data, a model accounting for the growth of the fibers from molecular to nano- and microscale is proposed.