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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