Off–On–Off fluorescence behavior of an intramolecular charge transfer probe toward anions and CO2

•ICT based tricyanoethylphenyl phenanthroimidazole (TCPPI) core containing organic scaffold•TCPPI showed naked–eye sensitive fluorescence “turn –on” response to detect selectively F- and CN- anions.•The anion activated probe TCPPI has also been utilized to sense CO2.

The photophysical behavior of a newly developed fluorescent probe, tricyanoethylphenyl phenanthroimidazole (TCPPI) has been studied. Upon interaction of different class of anions TCPPI displayed naked–eye sensitive fluorescence “turn–on” response to detect selectively F− (0.98 μM, 18.62 ppb) and CN− (1.12 μM, 29.12 ppb) anions in acetonitrile (MeCN). Job's plot analysis revealed a 1:1 binding stoichiometry between probe and anions. The spectral data analysis and 1H NMR titration studies suggested about the affinity of F− and CN− anions with moderately acidic − NH fragment of imidazolyl unit of probe through deprotonation and H-bonding interaction. Moreover, the anion activated probe upon interaction with CO2 revived photophysical properties of probe, “On-Off-On” type fluorescence and enabled anion-induced CO2 sensing in the medium.

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