A hydroxyl coumarin-chalcone-based fluorescent probe for sensing copper ions in plant and living cells

Copper ions are essential trace elements for living organisms. However, its excessive levels in the liver and kidneys may lead to severe health issues. Therefore, developing effective fluorescent probes for detecting copper ions is crucial. A hydroxyl coumarin chalcone derivative featuring a hydroxyl substituent has been developed as a fluorescent probe for monitoring Cu²⁺. The probe can selectively detect Cu²⁺ in aqueous solutions, exhibiting a visible color change from red to light yellow to the naked eye. This is accompanied by a quenching of the red fluorescence, with a limit of detection of 11.2 μM. By utilizing Fourier transform infrared spectroscopy, fluorescence spectral changes upon alternating addition of Cu²⁺ and ethylene diamine tetraacetic acid, high-resolution mass spectrometry, and Job's plot analysis, along with a comparison of properties to a structurally analogous compound lacking a hydroxyl substituent, we propose that the probe engages in a 1:1 coordination reaction between its hydroxyl, adjacent carbonyl groups and Cu²⁺. The probe was successfully employed for the quantitative determination of Cu²⁺ content in a variety of real water, beverage and plant samples. Furthermore, the probe exhibits excellent biocompatibility, emitting bright fluorescence under confocal microscopy, which allows for the monitoring of intracellular Cu²⁺ level fluctuations.