Oligothiophene-functionalized perylene bisimide system: Synthesis, characterization, and electrochemical polymerization properties

The novel perylene bisimides functionalized with oligothiophene substituents in the bay position of the perylene core N,N'-di(2-ethylhexyl)-1,7-di(thiophen-2-yl)perylene-3,4,9,10-tetracarboxylic acid bisimide (2a), N,N'-di(2-ethylhexyl)-1,7-di[(2,2')bithiophen-5-yl]perylene-3,4,9,10-tetracarboxylic acid bisimide (2b), and N,N'-di(2-ethylhexyl)-1,7-di[(2,2';5',2")terthiophen-5-yl]perylene-3,4,9,10-tetracarboxylic acid bisimide (2c) have been synthesized and fully characterized. As compared to the unsubstituted perylene bisimide (3), the UV-vis absorptions of 2a-c undergo a bathochromic shift along with considerable band broadening and a less pronounced vibronic fine structure. Moreover, efficient intramolecular electron transfer between the oligothiophene-donor and perylene-acceptor leads to remarkable fluorescence quenching of the perylene core. Cyclic voltammetry measurements of these compounds were performed and corresponding polymers from the monomers 2b and 2c were prepared by electrochemical polymerization. Both oligomers and polymers possess a facile reductive process, and their oxidation potential can be tuned by variation of the number of thiophene groups. These properties make them promising materials for optoelectrical devices such as molecular switches, solar energy harvesters, and supercapacitors for energy storage.