Abstract Herein, we report a highly selective dual responsive chemosensor for detecting iron ion. The structural characterization of synthesized compounds was investigated on the basis of UV–vis, FTIR, 1 NMR, 13 NMR and Mass spectral data. The sensitivity and selectivity of RDFB toward Fe 3+ among different metal ions was examined by absorption, fluorescence, FTIR and mass spectral studies. Complexing with Fe 3+ ion leads to spirolactam ring opening of RDFB and consequently causes a color variation from colorless to red. Fe 3+ -specific binding to RDFB afford a 53-fold enhancement in fluorescence intensity and strong absorption in the visible range. The 1:1 binding mode was proposed on the basis of absorption, FTIR and MS studies. The HOMO and LUMO energy gap for RDFB and RDFB-Fe 3+ complex were found to be 3.782 eV and 1.875 eV suggesting that the interaction of Fe 3+ to RDFB reduces the HOMO-LUMO energy gap of the complex and stabilizes the system. The association constant of newly synthesized compound to the receptor is found to be 1.13 × 10 5 M −1 which further implying the potential of RDFB to acts as a selective chemosensor for Fe 3+ ions. Furthermore the reversibility of complexation of RDFB to Fe 3+ was also studied by conducting experiments against EDTA.