Regio-Dependent Optoelectronic Properties of Oligomeric Peropyrenes

Accumulation of π-conjugated structures is a promising strategy for developing new optoelectronic materials. We report the synthesis and characterization of peropyrene oligomers in different connecting manners. For the synthesis of the oligomers, we employed a consecutive reaction protocol, the cross McMurry coupling, photocyclization, and aromatization reactions (MPA protocol), using 2,3-dihydro-1H-phenalen-1-one modified with solubilizing groups and dimeric 2,3-dihydro-1H-phenalen-1-one derivatives. The resulting oligoperopyrenes showed distinct optical properties depending on the connecting position between the peropyrene units. The oligomers with 1,1'(10)-junction showed characteristic emission bands, which are reminiscent of excimer formation in parent peropyrene, whereas the 2,2'(9)-connected oligomers showed absorption and emission bands similar to those of monomeric peropyrene. These results suggest that (i) the MPA protocol is an efficient method for constructing oligomeric peropyrenes and (ii) the connecting position between the peropyrene units has key importance in the intramolecular optoelectronic interaction of the oligomeric peropyrenes.