Aroyleneimidazophenazine: A Sensitive Probe for Detecting CN^- Anion and its Solvatochromism Effect

A novel electron-deficient heteroacene 15H-pyrazino[2:3′,4′]pyrrolo[1′,2′:1,2]imidazo[4,5-b]phenazin-15-one (1) has been successfully synthesized and characterized. Compound 1 can selectively recognize CN^- and F^- over other 10 anions including BF₄^-, PF₆^-, Cl^-, SO₄^2-, NO₃^-, I^-, H₂PO₄^-, ClO₄^-, Ac^-, and Br^- in CHCl₃/DMF mixed solvents with dual responses, including absorption signals and fluorescent "turn-off" effects. CN^- and F^- can be distinguished by the completely quenched fluorescence (for CN^-) and partially reduced fluorescence (for F^-). Especially, compound 1 exhibits higher sensitivity to CN^- than F^- with the response concentration as low as 5.0 × 10^-6 mol/L. Moreover, compound 1 shows very interesting solvatochromism effect, and the CHCl₃ solution of compound 1 is sensitive to triethylamine, and its emission could change from green to red upon the addition of triethylamine, which is attributed to the n-π intermolecular charge-transfer interaction.