An Efficient Fluorescent Probe Based on Triphenylimidazole End‐Capped Diketopyrrolopyrrole for Selective Detection of CN − and TFA Through On–Off–On Response

ABSTRACT A triphenyl‐imidazole end‐capped donor–acceptor type potential molecular probe 3 has been designed and synthesized. Probe 3 upon interaction with different classes of metal ions/anions and NPPs displayed high selectivity with CN − anion (LOD = 20.42 nM) through fluorescence “turn‐ Off ” response and a naked‐eye sensitive visible color change. Job's plot analysis revealed a 1:2 binding stoichiometry. The interaction of 3 .CN − with trifluoroacetic acid (TFA) showed reversible behavior wherein the intensity of the probe rejuvenated, fluorescence “turn On‐Off‐On response,” along with a change in color of the medium. The change in rate constants and fluorescence lifetime of the probe suggested that the interaction of probe with CN − occurred in two steps: H‐binding and deprotonation of – N H functions of imidazolyl units. The mode of binding of probe with CN − was confirmed by 1 H NMR, FTIR, and HRMS data. The potential application of molecular probe has been examined to detect the CN − , TFA, and TFA vapor on test paper strips. The smartphone‐based RGB analysis of paper strips also supported on‐site colorimetric detection of CN − . Probe shows good recovery percentage of CN − in real water sample analysis. The output emission using chemical inputs CN − and TFA mimics the function of an IMP logic gate.