An Anthracene‐imidazoanthraquinone Conjugate Exhibiting Ratiometric Fluorescence Turn – On Behavior with CN‐ and F‐ Anions

A new conjugate, 2‐(4‐(anthracen‐9‐yl) phenyl)‐[1,2‐d]imidazole‐1H‐anthraquninone (AQI) has been designed and synthesized as a molecular probe 4. The photophysical and electrochemical behavior of the probe in the absence and presence of different class of ions were examined in acetonitrile solution. The probe 4 with F‐ and CN‐ anions showed ratiometric fluorescence “turn – On” response due to variation in ICT processes. Cyclic voltammetry of probe exhibited reversible redox behavior wherein the band gap (Eg = 1240/lmax) of probe (DE = 3.220 eV) decreased (~ 2.583 eV) after the interaction with F‐ and CN‐ anions. The probe interacted with both anions in a 1:1 stoichiometry with good binding constants (KF‐ = 2.05×106 M‐1 and KCN‐ = 1.46×106 M‐1) and limit of detection/quantification (LOD/LOQ) in nM range. The probable complexes, 4+F‐/CN‐ upon interaction with trifluoroacetic (TFA) acid showed reversible behavior. The out emission of probe upon providing F‐ and TFA as a chemical inputs mimic the function of a memory device, write−read−erase−read functions and a molecular keypad lock system. The probe upon interaction with both F‐ and CN‐ anions showed a naked‐eye sensitive color change in solution and on test paper strips. Also, the probe showed sensitivity to detect the F‐ in toothpaste.