Highly Sensitive Coumarin-Pyrazolone Probe for the Detection of Cr3+ and the Application in Living Cells

3-(7-(Diethylamino)-2-oxo-2H-chromen-3-yl)-1-(4-phenylthiazol-2-yl)-1H-pyrazol-5(4H)-one (COPYR) was competently synthesized from methyl 3-(7-(diethylamino)- 2-oxo-2H-chromen-3-yl)-3-oxopropanoate and 2-hydrazino- 4-phenyl thiazole. The interactions of receptor COPYR with various ions were investigated through absorption and steady-state fluorescence spectral studies, respectively. The results reveal that the complexation of Cr3+ ions with COPYR results in 1:1 stoichiometry, which resulted in a quick color response from fluorescent green to colorless with significant quenching of fluorescence at 506 nm in dimethyl sulfoxide medium. Theoretical calculations (density functional theory) confirm the photophysical changes such as absorbance and emission spectral changes. Furthermore, the confocal imaging of A-549 cells clearly points out that the synthesized probe COPYR could be applied for detecting Cr3+ in living cells.