Solution and solid-state supramolecular aggregates of new chiral oligothiophenes: synthesis and spectroscopic characterization

In recent years, -conjugated oligomers have emerged as ideal organic semiconductors for various electronic and optoelectronic applications, thanks to the possibility to modulate their electronic and optical properties (charge and exciton transport, light absorption and emission, response to external stimuli), which depend not only on their chemical structure and the conformation assumed, but also on the nano/mesoscale organization in the solid state. (1) Chirality represents one of the most sophisticated expedients to control supramolecular aggregation of similar systems, in particular their interchain spacing and/or alignment. (2) Furthermore, chiral nanostructures may display various intriguing physicochemical properties, exploited for example in sensors able to discriminate enantiomers (3) and in circularly polarized (CP) light detectors (4, 5) or emitters (6). However, since most studies have concentrated only on inorganic chiral nanomaterials, the creation of chiral organic semiconductors may open new doors for optoelectronics. We decided to work with new oligothiophenes (-conjugated systems well known in optoelectronic devices) functionalized with some inexpensive alkyl chiral groups derived from natural sources, seeking self-assembly properties, which would ensure supramolecular chirality and the onset of extraordinary optical and electrical properties.In particular, we will describe: a) the synthetic route developed for the preparation of these oligomers; b) their spectroscopic characterization (UV-Vis, ECD, fluorescence) to investigate the supramolecular organization both in solution and in thin films (prepared by drop casting and spin coating techniques), in connection with standard and polarized optical microscopy analysis.