Dual‐Mode Fluorescence Modulation Using Ferrocene‐Dithienylethene–Pyromellitic Diimide‐Based Photoswitchable Material: Applications in Cascaded Molecular Logic and in Deciphering Secret Codes

ABSTRACT In the present study, we have developed a ferrocene‐pyromellitic diimide‐dithienylethene (Fc‐PmDI‐DTE)‐based multifunctional triad in a nonconjugated manner to achieve dual mode of fluorescence switching via photoinduced electron transfer (PET) and Förster resonance energy transfer (FRET) mechanism. The photoinduced reversible fluorescence switching was accomplished by the photoisomerization of DTE under irradiation of light with an excellent photocyclization and cycloreversion quantum yield in solution as well as solid state. At photostationary state (PSS), the cyclization conversion yield was found to be 94.3%, demonstrating the high efficiency of the photochromic process. Further, the PET mediated fluorescence switching of PmDI fluorophore was achieved via reversible oxidation and reduction of ferrocene (Fc) using Fe(ClO 4 ) 3 and sodium L ‐ascorbate (LAS). The feasibility of the PET process was further validated by Rehm‐Weller equation (ΔG = ‐3.049 eV) along with the density functional theory (DFT) calculations. Using different selective external agents such as Fe 3+ , LAS, and UV (ultraviolet), and visible light, we have utilized the output emission to construct a complicated binary logic gate by “AND”, “OR”, and “NOT” gates. Due to the excellent reversible photoswitching and fatigue resistance properties, our designed Fc‐PmDI‐DTE triad was successfully applied in deciphering secret codes, suggesting promising application in anticounterfeiting.