Targeting One Precise Aggregation-Induced Emission (AIE) Mechanism to Design Indolocarbazole-Based AIE-Active Phosphorescent Pt(II) Complex and Its Anion Sensing Property

AIE mechanisms of the restrained intramolecular rotation (RIR) and restrained molecular configuration transformation (RMCT) jointly contribute to the AIE nature of the Pt(II)(C^N)(N-donor ligand)Cl-type complex. However, focusing on one certain mechanism would provide more accessibilities to AIE molecular designs. Herein, by combining a rigid cyclometallating ligand 11,12-dibutyl-3-(pyridin-2-yl)-11,12-dihydroindolo[2,3-<i>a</i>]carbazole (ICZ-<i>o</i>-Py) with a rotational monodentate ligand 2-hydroxy-4-(pyridin-4-yl)benzaldehyde (L-SYQ), an AIE-active Pt(II) complex <b>Pt-ICZ-SYQ</b> receiving rigid coordination configuration of the Pt center is designed and synthesized. Theoretical and experimental results show that the RIR effect dominates the AIE mechanism. On the other hand, the salicylaldehyde group is selected as an ion response unit toward F^-. Accordingly, the F^- detection studies including the responses of absorption and turn-on emission, anti-interference ability, detection limits, sensing mechanism, and detections in the water environment as well as at solid state are fully covered. The sensing mechanism of -OH unit deprotonation is confirmed based on the ¹H NMR titrations, strong base reaction experiment, and theoretical calculations. Meanwhile, by taking advantage of its AIE characteristic, a solid-phase detection platform assisted by a smartphone is further developed. Eventually, these results should offer valuable clues for the mechanism study and molecular design of AIE organometallic complexes as well as for their potential application exploring.