A New Fluorescent Probe based on Carbazole-Benzopyranyl for the Recognition of ONOO^- and its Application

In this study, we successfully synthesized a colorimetric and photoluminescent fluorescent probe CBB by introducing benzopyran malononitrile at the 3-position of N-butylcarbazole and pinacol borate structure at the 6-position of N-butylcarbazole. The probe CBB characterized by a substantial Stokes shift (146 nm) demonstrates high selectivity and sensitivity to ONOO^-. The probe CBB can specifically identify ONOO^- by UV-Vis and fluorescence spectroscopic techniques. When ONOO^- is added to the solution of CBB, the solution's color transitions from orange to colorless in daylight, and from pink to blue under a 365 nm UV lamp, making these can be easily recognized by the naked eye. The recognition mechanism was validated using ¹H NMR, mass spectrometry (MS) and density functional theory (DFT) calculations. In addition, cell imaging experiments demonstrated that CBB effectively captured the fluorescence signals in both the red and blue channels of HeLa cells through fluorescence confocal microscopy, successfully identifying exogenous ONOO^- within these cells. These results show that the probe CBB possesses strong monitoring capabilities for ONOO^-, offering new opportunities for research and application in related fields.