Synthesis, Photophysics, and Electrochemistry of Tetra(2-thienyl)ethylene (TTE) Derivatives

We have synthesized a series of tetra(2-thienyl)ethylene (TTE) derivatives, selectively functionalized at the thiophene α positions, either by a coupling procedure or by direct electrophilic substitution of the TTE system. Optical spectroscopy revealed that TTE shows orange emission (470 nm) in a diluted 2-MeTHF matrix at 77 K and blue (420 nm) aggregation-induced emission (AIE) in the solid state. An exhaustive electrochemical study afforded a full rationalization of the electronic properties in terms of the HOMO and LUMO energy levels and gaps, as well as localization and features of the redox centers with respect to TTE functionalization.