A chromogenic “off–on” azomethine sensor possessing ONNNO receptor site for iron species and its application in the fabrication of INHIBIT type molecular logic gate

A Schiff base “off–on” chromogenic sensor bearing ONNNO receptor site for the encapsulation of iron species have been synthesized. The sensor is capable of detecting Fe2+ and Fe3+ metal ions, respectively, in organic and mixed organic aqueous media by naked eye. The photophysical properties of sensor were compared with its structural analogs (with different substituents and motifs). The sensor was found relatively efficient due to the presence of appropriate binding cavity formed by the donor set as well as role of the attached substituents in bathochromic and hyperchromic shift in UV–Vis spectrum. The detection limit for the naked eye sensing of Fe2+ and Fe3+ were 1 μM and 1.1 μM in methanol, respectively. The sensor showed colorimetric ‘off–on’ switch in the absence and presence of these metal ions (Fe2+ and Fe3+), respectively due to intermolecular charge transfer from electron rich receptor site to electron deficient metal center. Furthermore, it is useful for the fabrication of INHIBIT type logic gate on the basis of interference caused due to F− and CH3COO− ions. These anions interact with the donor set via non-covalent interactions and switch off the colorimetric response by reducing the charge transference. Hence, sensor can be applied for the fabrication of INHIBIT type molecular logic gate.

Graphical abstractA proficient “off–on” chromogenic Schiff base chemosensor for Fe2+ and Fe3+ has been developed. An INHIBIT type logic gate at molecular level is also fabricated for this sensor.Figure optionsDownload full-size imageDownload as PowerPoint slide