A simple and effective fluorescent chemosensor for the cascade recognition of Zn2+ and H2PO4− ions in protic media

The chiral Schiff base N-(2-hydroxy-1-naphthyl)methylidene-(S)-α-phenylethylamine (1) was designed and synthesized as a fluorescent chemosensor based on the photoinduced electron transfer (PET) and CN isomerization mechanisms. The receptor exhibited a highly selective switch-on fluorescence response toward Zn2+ and especially avoided the interference of Cd2+ when the detection was conducted in unbuffered methanol solution. Furthermore, the in situ generated 1·ZnII-complex could be employed for the specific recognition of H2PO4− by fluorescence turn-off signaling through a ligand displacement process.