A nitrobenzoxadiazole (NBD)-appended calix[4]arene conjugate (L) possessing a cyclic core formed by connecting the 1,3-positions at the lower rim has been designed. The L has been developed as a receptor for the selective recognition of biologically and ecologically relevant trivalent metal ions, viz., Cr 3+ , Fe 3+ , and Al 3+ . The interaction and region of binding of these metal ions by the receptor L have been explored by isothermal titration calorimetry, spectroscopy, microscopy, and density functional theory (DFT) computational studies. The probe L itself exhibits weak fluorescence emission intensity, and the quantum yield is enhanced by ∼4-fold upon addition of the M 3+ ion due to the chelate enhanced fluorescence effect. Fluorescence enhancement also takes place in L when it interacts with M 3+ even in the solid state and in the MCF7 cancer cells. The binding constant (K b ) for M 3+ by L is ∼10 4 M -1 , supporting that these ions bind to L with moderate strength. The detection limit for all the three metal ions is as low as 4-5 μM. The 1 H NMR data reflects the region of binding of the M 3+ ion to L. The binding is further supported by DFT studies where the space filling structures evidently shows the binding core in L, and the M 3+ ion is buried in this core. As a result of this, the microscopy features are almost the same for L and {L + M 3+ }. The reversible utility of the sensor has been achieved by the addition of H 2 PO4- Based on the input-output information, a molecular logic circuit (INHIBIT logic gate) has been built, which will provide an electronic basis for designing a memory device by the concerned experts.