Herein, we present a family of 7‐(diethylamino)coumarin‐3‐carboxamides, bearing three different aza‐crown moieties (chelating unit). All synthesized compounds have shown a colorimetric response and fluorescence ON–OFF behavior to the presence of lead, calcium, magnesium, and copper, with higher affinity toward the latter, even in the presence of other cations in solution. Optical spectroscopies, X‐ray crystallography, and EPR experiments show that Cu(II) induces an irreversible oxidation on the coumarin core, with the concomitant formation of Cu(I) and an organic radical species. The emergence of an absorption band in the visible region upon radical formation results in the appearance of blue color, which fades over time, highlighting the potential of these sensors for rapid detection of copper(II) ion under the naked eye.
Gomes et al. (Sun,) studied this question.
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