Sequential colorimetric recognition of Cu²⁺ and CN^- by asymmetric coumarin-conjugated naphthol groups in aqueous solution

A new chemo-sensor (E)-4-((2-((2-hydroxynaphthalen-1-yl)methylene)amino) phenyl-amino)-3-nitro-2H-chromen-2-one (1) based on the combination of 2-hydroxy-1-naphthaldehyde and precursor 4-((2-aminophenyl)amino)-3-nitro-2H- chromen-2-one was designed and synthesized as a selective colorimetric sensor for Cu²⁺. 1 exhibited a color change from yellow to orange in the presence of Cu²⁺ in aqueous solution and the resulting 1-Cu ²⁺ complex sensed cyanide through naked eye. Moreover, 1 could be used as a practical, visible colorimetric test strip for Cu²⁺ in aqueous environment. These results demonstrate a new type of the sequential recognition of Cu²⁺ and CN^- by a convenient, easy and colorimetric method.