A Novel Imidazophenazine-Based Stimuli Responsive Chemosensor for Highly Selective and Sensitive Fluorescence Detection of CN–

A fluorescent imidazophenazine-based derivative (S) has been successfully synthesised, and can be used as a chemsensor for relay recognition of CN– in DMSO/H2O (7 : 3, v/v) solution, which exhibited external stimuli-responsiveness. The sensor immediately responded with obvious colour changes (from red to purple) and fluorescent quenching when CN– was added to the S solution. Its detection limit for CN– is 2.16 × 10−7 M. In addition, NMR spectroscopy and density function theory calculations were also used to confirm the recognition mechanism. In particular, the fluorescence responding circle could be repeated three times by the sequential addition of CN– and CH3COO– or CN– and HSO4–. Moreover, a CN– detection test paper was prepared using S, providing a convenient method for CN– identification.