Molecular self-assembly and fluorescence change of donor-acceptor cocrystal based on naphthalimide derivatives

Organic cocrystals formed by two or more components through π-π interactions, charge transfer, and hydrogen/halogen bondings have attracted extensive attention because of their applications in the field of organic optoelectronics. Here, we prepared three charge-transfer cocrystals by solution-process self-assembly method which used Coronene and pyrene as donors, N,N′-dimethyl-1,4,5,8-naphthalenetetracarboxylic diimide (NDI-1) and N,N′-bis(ethyl)-1,4,5,8-naphthalenetetracarboxylic diimide (NDI-2) as acceptors. Detailed structural characterizations clarified the mixed stacking mode in the charge-transfer cocrystals, and the supramolecular network was stabilized by C–H···O hydrogen bonds and π-π interactions. Interestingly, compared with the original donors, three cocrystals show different fluorescence emissions, which is related to the formation of charge-transfer states between donors and acceptors. This cocrystal strategy provides a new opportunity for the design of new organic light-emitting charge-transfer complexes.