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In consideration of the nucleophilic capacity of thiophenols, which could cleave sulfonamide bond under neutral conditions, a cyclometalated iridium(III) complex (probe 1) comprised 2,4-dinitrobenzenesulfonamide (DNBS) as the recognition unit was designed and synthesized to high selectivity and sensitivity detect thiophenols successfully based on internal charge transfer (ICT) mechanism. Upon addition with thiophenols to 20% DMSO/PBS solution of nearly non-fluorescent probe 1 (10 μM, pH = 7.4), fluorescent product (complex 2) was formed after cleavage of DNBS group and a significant emission enhancement at 470 nm was observed. In addition, it could be successfully applied to detect thiophenol in water samples with a high recovery, confirming its practical value in environment science.

A novel cyclometalated iridium(III) complex 1oo including two photochromic diarylethene (DTE) units and 2,4-dinitrobenzenesulfonyl (DNBS) group was designed and synthesized as a probe for thiophenol. Due to the intramolecular charge transfer (ICT) mechanism, probe 1oo displayed almost non-fluorescence. After nucleophilic elimination reaction occurred triggered by thiophenol a fluorescence complex 2oo was generated, the ICT process was blocked and obvious fluorescence enhancement centred at ca. 450 nm was observed. Moreover, during the detection process, fluorescent behavior of probe 1oo could be modulated upon alternate irradiations of UV and Vis light, ascribed to photochromic diarylethene molecules in the C^N ligands could play the part of fluorescent switch. Probe 1oo exhibited excellent sensitivity (LOD: 2.43 μM), selectivity and rapid response (15 min) to thiophenol.