An overview on AIEgen-decorated porphyrins: Current status and applications

One of the major obstacles of porphyrins is the aggregation-caused quenching (ACQ) of photoluminescence due to the strong intermolecular pi-pi interaction of the planar porphyrin core in the solid state. However, ACQ leads to the nonradiative deactivation of the photoexcited states which results in short-lived charge-separated states and thus low photoluminescence and singlet quantum yields. This phenomenon would limit the utilization of porphyrins in near-infrared fluorescent bioimaging, photodynamic therapy, photocatalytic hydrogen evolution, electrochemiluminescence, and chiroptical applications. Hence, to address the ACQ property of porphyrins and enhance the performance of the above applications, a limited number of AIEgen-decorated porphyrins have been designed, synthesized, and tested for their applications. It has been found that the introduction of AIEgens, such as tetraphenylethylene, diphenylacrylonitrile, (3,6-bis-(1-methyl-4-vinylpyridinium)-carbazole diiodide, and iridium motif into the porphyrin core, transformed the porphyrins from ACQ to aggregation-induced emission (AIE) in their solid state due to the reduced strong intermolecular pi-pi stacking of porphyrins. Consequently, such porphyrins containing AIE features are employed as potential candidates in the above-mentioned applications. In this review, we summarize the AIEgen-decorated porphyrins which have been published to date, and also discuss the benefits of converting porphyrins from ACQ to AIE for enhanced performance within each application. As far as we know, there is no review that summarizes the structures and applications of AIEgen-decorated porphyrins to date. Therefore, we presume that this review would be helpful to design more efficient AIEgen-decorated porphyrins for a wide range of applications in the future.