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.

在先前的研究中，我们观察到二氰基异佛尔酮衍生物表现出显著的聚集诱导发光（AIE）行为。为探究这些具有AIE/AIEE特性的发色团在生物成像领域的应用潜力，本研究将氰基中的酯基替换，从而形成基于异佛尔酮的新系列化合物（2a–2e）。其中，2a–2d展现出明显的AIE/AIEE现象，而2e在聚集体状态下则表现出荧光猝灭。通过扫描电子显微镜（SEM）和动态光散射（DLS）技术，我们研究了不同含水率下聚集体的形态和尺寸，发现大量平均直径在78.79–392.7 nm范围内的球形或四方形纳米颗粒与这些AIE/AIEE或ACQ行为密切相关。我们还对这些化合物在不同状态下的光学性质进行了比较分析。晶体数据表明，2a–2d的多个分子内和分子间相互作用导致分子构象更加稳定，增加了化合物的平面性，限制了分子内运动，并促进了J型聚集体的形成，使得发色团2a–2d在固态下能够发出强烈的荧光。此外，通过密度泛函理论计算的分子前线轨道能量和带隙与实验结果高度一致。最终，这些AIE/AIEE活性化合物在生物成像领域的应用前景广阔，为某些AIE/AIEE系统的应用提供了全新的策略。