Systematic Study and Imaging Application of Aggregation-Induced Emission of Ester-Isophorone Derivatives

The dicyanoisophorone derivatives show obvious AIE behaviors in our previous work. To study the bioimaging application of these chromophores with AIE/AIEE properties, the ester groups substituted for one cyan to form a new family based on isophorone (2a–2e). 2a–2d exhibit obvious AIE/AIEE phenomena, while 2e shows fluorescence quenching in the aggregate state. The morphology and size of aggregates with different water contents were investigated using SEM and DLS, indicating that a large number of smaller globular or quadrate nanoparticles with average diameters in the range 78.79–392.7 nm in mixed solutions are related to these AIE/AIEE or ACQ behaviors. We also made comparative analyses of their optical properties in different states. The crystal data of 2a–2d reveal that the multiple intra- and intermolecular interactions leads to the molecular conformation being more stable, increases the planarity of compounds, restricts the intramolecular motions, and promotes the formation of J-type aggregate, enabling chromophores 2a–2d to emit intensely in the solid state. In addition, the frontier molecular orbital energy and band gap calculated by density functional theory are quite consistent with the experimental results. Finally, these AIE/AIEE-active compounds could be used in bioimaging applications, which immensely provide a new strategy to the application of some AIE/AIEE systems.