Vinyl Groups Containing Tetraphenylethylene Derivatives as Fluorescent Probes Specific for Palladium and the Quenching Mechanism

Main observation and conclusion We previously reported that a series of tetraphenylethylene (TPE)‐containing all‐hydrocarbon conjugated polymers exhibited a specific fluorescence quenching by palladium ions (Pd2+). To understand the quenching mechanism, herein we investigate the quenching behaviors of three TPE derivatives in the presence of Pd2+. Each TPE derivative, consisting of TPE unit and terminal vinyl groups, shows an aggregation‐induced emission (AIE) and its fluorescence turns off specifically to Pd2+. The sensitivity is enhanced with increasing numbers of vinyl groups in the molecules. By time‐resolved fluorescence measurement, a dynamic quenching is observed where the fluorescence lifetime is reduced with Pd2+. Specifically, the quenching occurs via the electron transfer in the excited states, as suggested by the disappearance of the stimulated emission band in transient absorption spectra. A theoretical calculation on the excited states identifies intermolecular electron transfer from TPE derivatives to Pd, especially for electron–rich TPE derivative. The mechanism can be general for the design of novel AIE active chemosensors. We report fluorescent probes specific for palladium based on tetraphenylethylene (TPE) and the dynamic quenching mechanism via the electron transfer between TPE derivative and palladium.