A near-infrared AIE-active Ir(III) complex for dual detection of viscosity and bisulfite in living cells.

Sulfur dioxide and its physiological forms bisulfite (HSO3-) and sulfite (SO32-), along with intracellular viscosity, are involved in regulating many physiological processes and are closely related to diseases and cancer development. Therefore, developing probes capable of selectively responding to HSO3-/SO32- and viscosity is of great significance and practical application value for exploring the pathological mechanism of related diseases and realizing early biological detection. An aggregation-induced near-infrared emission-based Ir(III) complex probe named Ir-TH was designed and synthesized, in which the ester-linked thiophene unit serves a dual role: it not only acts as an AIE-active rotor to track viscosity changes through the restriction of intramolecular rotation but also provides the supramolecular binding sites for HSO3-. The probe exhibits a high sensitivity and selectivity toward viscosity, good photostability, and a favorable luminescent response to HSO3- with a fast response time (5 min), low detection limit (0.022 μM, 3σ/k) and wide linear range (0-80 μM). Moreover, Ir-TH can specifically track changes in intracellular HSO3-, as well as monitor dynamic changes in intracellular viscosity during ferroptosis, providing a valuable reference for the construction of multifunctional sensors.