Electron deficient imine-based receptor for selective colorimetric recognition of cyanide ion through aromatic CH•••anion interactions

Abstract

An electron withdrawing natured di-nitro substituted, imine based receptor L has been designed and synthesized. Naked-eye colorimetric experiment and UV–vis spectrometric studies reveals that the receptor L selectively binding the cyanide anion through C–H•••cyanide interaction. On the other hand, benzene analogue of receptor does not show any color and spectral change with cyanide ion. Though the receptor L do not have any strong traditional hydrogen bonding donor moieties, the obtained exclusive selectivity of L towards cyanide can be explained with help of Hay et al. theoretical postulates. Electron withdrawing natured functionalizations on the aromatic moiety of L is significantly enhanced the strength and selectivity of anion sensor L. Particularly, upon nitro substitution at 2nd and 4th phenyl ring of L, the un substituted aromatic –C–H groups are rehabilitated into relatively more acidic i.e. The aryl group having nitro functionalities that contributes to selective anion binding in cyanide complex of L through CH•••cyanide ion interactions. Detailed molecular electrostatic potential (MEP) map analysis supports our spectroscopy findings. To the best of our knowledge this is a first report of colorimetric sensing of cyanide majorly inclined by non-traditional aromatic-C–H•••cyanide interaction.

Keywords

• Anion receptors
• Anion–π interaction
• Colorimetric anion sensor
• Cyanide sensors