One‐Pot Synthesis and Excited‐State Dynamics of Null Exciton‐Coupled Diketopyrrolopyrroles Oligo‐Grids

Abstract

AbstractExciton coupling in molecular aggregates plays a vital role in impacting and fine‐tuning optoelectronic materials and their efficiencies in devices. A versatile platform to decipher aggregation‐property relationships is built around multichromophoric architectures. Here, a series of cyclic diketopyrrolopyrrole (DPP) oligomers featuring nanoscale gridarene structures and rigid bifluorenyl spacers are designed and synthesized via one‐pot Friedel–Crafts reaction. DPP dimer [2]Grid and trimer [3]Grid, which are cyclic rigid nanoarchitectures of rather different sizes, are further characterized via steady‐state and time‐resolved absorption and fluorescence spectroscopies. They exhibit monomer‐like spectroscopic signatures in the steady‐state measurements, from which null exciton couplings are derived. Moreover, in an apolar solvent, high fluorescence quantum yields and excited‐state dynamics that resembled DPP monomer are gathered. In a polar solvent, the localized singlet excited state on a single DPP dissociates into the adjacent null coupling DPP with charge transfer characteristics. This pathway facilitates the evolution of the symmetry‐broken charge‐separated state (SB‐CS). Notable is the fact that the SB‐CS of [2]Grid is, on one hand, in equilibrium with the singlet excited state and promotes, on the other hand, the formation of the triplet excited state with a yield of 32% via charge recombination.