Fluorescent multifunctional pyridine-functionalized Coumarin-fused imidazole: Ratiometric dual-mode probe for metal...

Coumarin is a notable fluorophore with many advantages, such as high fluorescence quantum yield, large Stokes shift, good photostability, and low toxicity. The development of chemosensor which is capable of recognizing specific ion in selective manner will be the challenging task for many researchers. In this study, the pyridine-functionalized coumarin-fused imidazole derivative was successfully synthesized, characterized, and evaluated for various photophysical studies including solvent effect, metal ion and pH sensing studies. The probe selectively detects Zn²⁺, Cu²⁺ and Ni²⁺ with metal ion specific optical output. The binding mechanism of the probe with metal ion was investigated through Job's plot, Benesi-Hildebrand plot and mass spectrometry. Additionally, the probe-Zn²⁺ ensemble exhibited intriguing ratiometric spectral reversibility in the presence of adenosine triphosphate (ATP), functioning as a fluorescence "on-off" sensor. Additionally, the probe exhibited specific pH sensing in the acidic region, displaying a color change from pale yellow to intense yellow under UV light, attributed to a charge transfer process. This study highlights the potential of combining coumarin with heterocyclic derivatives to create a multifunctional fluorescent probe.