Achieving Diversified Emissive Behaviors of AIE, TADF, RTP, Dual-RTP and Mechanoluminescence from Simple Organic Molecules by Positional Isomerism

Organic emitters with multiple emissions such as aggregation-induced emission (AIE), thermally activated delayed fluorescence (TADF), room-temperature phosphorescence (RTP), and mechanoluminescence (ML) are promising candidates for various high-tech applications but still very rare. Here, for the first time, an effective strategy of positional isomerism is applied to obtain simple organic isomers featuring diversified emissive behaviors of AIE, TADF, RTP, dual-RTP, and ML. In Particular, simultaneous AIE, TADF, and ML are successfully realized in the ortho-isomer o-ClTPA while typical AIE and unique dual-RTP coexist in the para-isomer p-ClTPA. Crystal structure analysis shows that the subtle variation in the substitution position can significantly alter intermolecular interactions and molecular packings, which in turn exerts remarkable effects on crystal-state emissive properties. Therefore, diversified emissive behaviors of TADF, RTP, dual-RTP, and ML are consequently observed from these positional isomers. Furthermore, theoretical calculations not only afford deep insight into the mechanism of different luminescent properties but also elaborate the relationship between positional isomers and luminescent properties from molecular and crystalline perspectives. These simple isomers featuring diversified emissive behaviors of AIE, TADF, RTP, dual-RTP, and ML are reported for the first time, which will deepen the understanding of the relationship between molecule structures and multiple emissions.