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

A novel electron-deficient heteroacene 15H-pyrazino[2″,3″: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−, SO42−, 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.