A near-infrared AIE-active Ir(III) complex with a super-large stokes shift and efficient singlet oxygen generation

Abstract

Iridium complexes have shown broad applicability across various fields, particularly in bioimaging and photodynamic therapy owing to their exceptional photophysical properties. However, their effectiveness in biological applications is often constrained by aggregation-caused quenching (ACQ), which reduces luminescence efficiency, impairs precise targeting, and lowers singlet oxygen generation. Herein, this study report the design and synthesis of a novel trifluoromethylated cationic cyclometalated Ir(III) complex incorporating diphenylamino (DPA) and trifluoromethyl groups, which exhibits desirable Aggregation-Induced Emission (AIE) characteristics, an ultra-large Stokes shift, and near-infrared (NIR) emission. Comprehensive structural and photophysical analyses, including single-crystal X-ray diffraction and transmission electron microscopy, reveal that these Ir(III) complexes exhibit strong aggregation behavior, significant π-π and C-H···F interactions, and remarkable oxygen sensitivity in ethyl cellulose (EC) films ($K_{\mathrm{SV}}^{\mathrm{app}}$= 0.05586 Torr^-¹). Notably, the DPA-modified complex Ir3 enhances singlet oxygen generation within intracellular environments, exhibiting distinct phototoxicity and minimal dark toxicity against Henrietta Lacks (HeLa) cells. This work advances the design strategy for AIE-active Ir(III) complexes for photodynamic therapy (PDT) and oxygen sensing, providing insights into developing functional materials with enhanced NIR emission, large Stokes shifts, and selective bioimaging capabilities. These findings lay a promising foundation for further application of Ir(III) complexes in cancer phototherapy and other biomedical fields.