Highly selective and sensitive colorimetric probes for Cu2+ ions based on ethoxyaniline croconaine dyes.

[Display omitted] • Croconaine dye based chemosensors ONKT and PNKT for Cu2+ detection were synthesized. • ONKT and PNKT are highly sensitive and selective colorimetric probe toward Cu2+. • The effect of ethoxy group of croconaine dye on Cu2+ ion recognition was discussed. • Possible recognition mechanism of ONKT and PNKT for Cu2+ was also proposed. Two highly sensitive and selective colorimetric ethoxyaniline croconaine dye probes, (E)-2-((2-ethoxyphenyl)amino)-5-((2-ethoxyphenyl)iminio)-3,4-dioxocyclopent-1-en-1-olate (ONKT) and (E)-2-((4-ethoxyphenyl)amino)-5-((4-ethoxyphenyl)iminio)-3,4-dioxocyclopent-1-en-1-olate) (PNKT) for sensing of Cu2+ ion have been synthesized and characterized. Compared with other metal cations tested, the colorimetric behavior of the probes is significantly different in the presence of Cu2+ ions. When Cu2+ ions were added, the colors of ONKT and PNKT changed from orange to colorless, and the absorbance at the maximum absorption wavelength decreased obviously. The probes have been proved to be sensitive, selective, linear and low in detection limit for Cu2+ ions. In addition, with Cu2+ and EDTA as input signals and the absorption intensity of ONKT at 500 nm as output signal, ONKT is designed as a molecular logic gate with storage and deletion functions. Therefore, these probes provide a new colorimetric method for qualitative and quantitative selective detection of copper ions. [ABSTRACT FROM AUTHOR]