A highly selective and reversible chemosensor for cyanide and pH detection was developed based on intramolecular NH···NH2 hydrogen bonding.

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A new fluorescent ''turn-on'' cyanide chemodosimeter 5 was developed for the first time based on the irreversible deprotonation/oxidation of the CH group followed by the reversible deprotonation of the NH group, with high selectivity and dramatic red-shifted absorption (E263 nm). The photoinduced electron transfer (PET) is prevented by the irreversible process, which results in coplanar geometry between indole and naphthalimide causing enhancement of fluorescence. Fig. 1 Promoted strategy for sensing anions.

The cis- and trans-configurational isomers of 3 are designed and investigated as chemodosimeters for CN(-) ions for the first time. The cis-3 reveals a NIR absorbance at 717 nm (vs. trans-3, 620 nm), and such a configurational difference can be attributed to the acidity as well as position of the binding site (CH group). A probable sensing mechanism involving cyanide-driven carbanion electron-transfer oxidation is proposed.

We developed a new chromogenic and fluorescent 'turn-on' chemodosimeter 1 based on a F(-)-triggered cascade reaction. This system displayed significant changes in UV/vis absorption and fluorescence emission intensities selectively for F(-) over other anions in a mixture of CH3CN/H2O(95 : 5, v/v) and in acetonitrile.