A new carbazole-based Schiff-base as fluorescent chemosensor for selective detection of Fe3+ and Cu2+

A new carbazole-based Schiff-base (1) as a multi-functional fluorescent chemosensor was designed, synthesized and characterized, which can selectively recognized Fe3+ and Cu2+ ions over a number of other metal ions. Compound 1 could detect Fe3+ and Cu2+ by UV–Vis method and fluorescence method. The stoichiometry ratio of 1-Fe3+ and 1-Cu2+ are 2:1 and 1:1, respectively, by the method of Job’s plot. Moreover, the detection limits were calculated to be 4.23 × 10−6 mol/L for Fe3+ ion and 5.67 × 10−6 mol/L for Cu2+ ion. In the presence of Fe3+/Cu2+ ions, the fluorescence enhancement was attributed to the inhibited CN isomerization and the obstructed excited state intramolecular proton transfer (ESIPT) of compound 1. At the same time, the interactions of compounds 1 with other ions were also investigated and unobvious UV–Vis absorption and fluorescence spectral changes were observed. Thus a new kind of chemosensor for Fe3+/Cu2+with high sensitivity and selectivity was introduced.

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► We designed and synthesized a new carbazole-based Schiff base sensor.
► Compound 1 could be used as a multi-functional sensor for detecting Fe3+/Cu2+ by both using UV–Vis and fluorescence methods.
► We found that the bonding mode between compound 1 and Fe3+/Cu2+ is different.