Aggregation-induced emission (AIE) is a powerful strategy for developing highly emissive materials in the condensed phase; however, general molecular design principles remain limited. Here we propose an “AIE Tag” concept, in which an AIE-active unit is covalently appended to a conventional π-conjugated fluorophore to introduce fluorescence quenching in solution and thereby generate AIE behavior. Unlike conventional approaches based on intrinsically AIE-active cores, this strategy enables modular conversion of pre-existing fluorophores without redesigning their electronic structures. Using tetraphenylethene (TPE) as a model tag, we investigated oligophenylene, diphenylanthracene (DPA), and perylene (Pe) derivatives. Spectroscopic and theoretical analyses suggest that TPE introduces an additional nonradiative decay pathway associated with a conical intersection (CI) localized on the TPE unit when the excited-state electronic density extends over the π framework. In the DPA series, structural relaxation appears to facilitate access to the CI, resulting in efficient fluorescence quenching in solution, whereas in the perylene series the CI is energetically inaccessible, leading to only partial quenching. These results suggest that the effectiveness of the AIE Tag strategy is influenced by the energetic accessibility of the TPE-derived CI, providing mechanistic insight into the operation of the AIE-tag concept and useful guidance for the future design of modular AIE systems.
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