An iridium complex-based phosphorescent probe for recognition to bisulfite and cyanide in neutral aqueous system

摘要

A newly designed cyclometalated iridium complex Ir(mepi)(ppy)_2 (2, Hppy=2-phenylpyridine, Hmepi=3,3-dimethyl-1-ethyl-2-(4-(pyridin-2-yl)styryl)indolium iodide (1)) was successfully synthesized for the rapid detection of HSO_3~- and CN~-. For complex 2, it is interesting that the selective 1,4-addition reaction with HSO_3~- in aerated DMSO/PBS buffer can be visualized by intense turn-on green emission. However, the 1,2-addition reaction with CN~- resulted in an emission color change from colorless to orange-yellow. Furthermore, the limits of detection for HSO_3~- and CN~- were calculated as low as 0.049 and 0.15 μM, respectively. The results indicate that the two anions can be detected selectively and separately by naked-eyes in neutral aqueous system. As the typical interfering anion for detecting HSO_3~-, HS~- led to the almost similar emission change that was caused by HSO_3~-. As a result, the reaction between 2 and HS~- could be assigned as 1,4-addition rather than 1,2-addition reaction, which was further confirmed by the ~1H NMR spectra changes of the ligand with these representative anions (HSO_3~-, HS~- and CN~-).