Positional isomers of cyanostilbene: two-component molecular assembly and multiple-stimuli responsive luminescence

An understanding of the aggregates and properties of positional isomers can not only uncover how a slight difference in molecular structure alter crystal packing and bulk solid-state properties, but also plays an important role in developing new types of molecule-based functional materials. Herein, we report a study of the molecular packing and static/dynamic luminescence properties of three cyanostilbene (CS)-based isomers (CS1, CS2, CS3) within their single- and two-component molecular solids. Changing the positions of the cyano substitutents in the CS isomers has a marked influence on their packing modes and luminescent properties. Moreover, two-component CS-based materials have been constructed, which exhibit tunable conformations and packing fashions, as well as fluorescence properties, which differ from the pristine CS solids. The CS-based two-component molecular materials show solvent-responsive luminescence due to the dynamic disassembly of the samples. Moreover, it was found that the system based on CS2 and octafluoronaphthalene shows reversible photochromic fluorescence upon alternating light illumination and grinding. Such co-assembly procedures provide a facile way to fabricate patterned luminescent film materials. Therefore, this work not only affords new insight into the relationship between isomers and luminescence from molecular and supramolecular perspectives, but provides an effective strategy to develop multiple-stimuli-responsive luminescent materials.