Naphthalene diimide cocrystals: A facile approach to tune the optical properties

Abstract

Core-substituted naphthalene diimides are attracting much interest because of their tunable optical properties, which are generally achieved by the elaborate introduction of electron-donating groups into electron-deficient core to form donor–acceptor compounds through the covalent bonds. Here we report that the optical properties of core-unsubstituted naphthalene diimides can be modulated by a facile cocrystal strategy. Based on the X-ray crystallographic and Hirshfeld surface analyses, the π–π interactions have been demonstrated to be the most important factor that answers for the optical properties of naphthalene diimide cocrystals, while other interactions, such as hydrogen bonds and solvation effects, have little impact on their properties but influence π stacking. This insight is of considerable significance for the development of naphthalene diimide based materials in various directions.