“Off–on–off” type of selectively pH-sensing 8-hydroxyquinoline-substituted gallium(iii) corrole†
We herein report the synthesis and pH-sensing properties of novel gallium corrole derivatives based on 8-hydroxyquinoline. The free base corrole and its gallium corrole derivatives were fully characterized using NMR spectroscopy and mass spectrometry. Their photophysical and electrochemical properties were also investigated using UV/Vis spectroscopy, fluorescence spectroscopy, MCD spectroscopy and cyclic voltammetry. A Ga-corrole derivative showed a good fluorescence response to change in pH in a wide pH range, from pH 1 to 12. Specifically, its fluorescence gradually diminished, from a high intensity at neutral pH, as the pH was either decreased or increased, i.e., into acidic and basic conditions, respectively. These results indicated that the Ga-corrole derivative would be able to serve as an efficient “off–on–off” fluorescent sensor of pH in the solution state.