Multicolor Emissions by the Synergism of Intra/Intermolecular Slipped π-π Stackings of Tetraphenylethylene-DiBODIPY Conjugate

Luminescent materials with tunable optical properties are of great importance for their potential application in the fields of optical-recording systems, sensors, security materials, informational displays, and molecular machines. To date, tuning double-color luminescence is easy to realize in many stimuli-responsive organic materials, while multicolor luminescence is very scarce. Herein, three new TPE-BODIPY conjugates, composed of a tetraphenylethylene (TPE) core bearing BODIPY units, were synthesized. The TPE-BODIPY 1 conjugate bearing two neighboring BODIPY units could emit strong fluorescence up to 100% quantum yield and multicolor light from green, to yellow, to red (GYR) both in solutions and in poly(methyl methacrylate) films with aggregation of it. Moreover, the GYR multicolor emissions in solution could interconvert by adding and removing THF. The crystal structure of the compound disclosed that two BODIPY units were completely perpendicular to the phenyl ring of the TPE core but parallel with each other. This extraordinary conformation resulted in intra/intermolecular slipped pi-pi stackings and even the synergism of these two slipped pi-pi stackings, giving the compound multicolor fluorescence. In contrast, two other TPE-BODIPYs, 2 and 3, had no intramolecular pi-pi stacking and only displayed green and yellow emission.