Intriguing Optical Properties due to the Intermolecular Interaction between AIE and ACQ Materials

To take advantage of the respective strengths of aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) materials, in this paper a unique approach is taken which is that tetraphenylethene and triphenylamine (classical AIEs), borondipyrromethene and benzothiadiazole (classical ACQs) are selected to construct AIE@ACQ bimolecular systems by simple compounding method, focusing on the effects on optical properties such as fluorescence, photothermal therapy, phosphorescence, and photodynamic therapy. Above all, the mechanisms and laws of the system are preliminarily found. First, AIEs and ACQs must, respectively, have electron-acceptor and electron-donors to form an intermolecular push-pull structure to ensure that the two molecules are close to each other, and intermolecular pi-pi stacking interaction separates the highest occupied molecular orbitals and lowest unoccupied molecular orbitals to reduce Delta E-st, causing intriguing optical properties. Second, the matching degree of the conjugate structure between AIEs and ACQs is also an important factor. Utilizing these systems, it is found that different structural compositions possess different optical synergy properties, so different AIE@ACQ bimolecular systems can be constructed according to the actual needs, which have the advantages of efficiency and convenience, providing a new idea for the united application of AIEs and ACQs.