A new rhodamine-based fluorescent chemosensor (1) for transition metal cations was synthesized by one-step facile condensation of rhodamine B and 2-aminopyridine. Without metal cations, 1 is colorless and nonfluorescent, whereas addition of metal cations (Fe3+, Hg2+, Pb2+, and Fe2+) leads to an obvious color change to pink and an appearance of orange fluorescence.
![Spiro[1H-isoindole-1,9'-[9H]xanthen]-3(2H)-one,3',6'-bis(diethylamino)-2-phenyl- Structure](https://image.chemsrc.com/caspic/227/38660-35-4.png)