Two-component molecular cocrystals of 9-acetylanthracene with highly tunable one-/two-photon fluorescence and aggregation induced emission

Abstract

Adjusting and controlling the solid-state photophysical properties of molecule-based fluorophores are crucial for the development of next-generation luminescent materials. In this work, we report the tunable photoemission of a 9-acetylanthracene (ACA) chromophore based on the formation of two-component molecular cocrystals with four different co-assembled building blocks (4-bromotetrafluorobenzene carboxylic acid, 2,3,5,6-tetrafluorohydroquinone, octafluoronaphthalene, and 1,2,4,5-tetracyanobenzene (TCB)), which present wide-range tunability of luminescence properties (such as wavelength, color, fluorescence lifetime, photoluminescence quantum yield and two-photon emission) relative to pristine ACA. In addition, aggregation induced emission (AIE) properties can be further obtained for ACA.TCB cocrystals, which are absent for the pristine ACA solid. Moreover, density functional theory (DFT) calculations suggest that the introduction of TCB can largely influence the energy level structures and orbital distributions of the ACA chromophore in the two-component crystals. Therefore, by the combination of experimental and theoretical studies on the molecular cocrystals, this work not only reports the supramolecular assembly of new types of crystalline two-component ACA systems, but also provides a detailed understanding of the structure–property relationship between molecular aggregation and luminescence behaviors.