A Cr(VI) selective probe based on a quinoline-amide calix[4]arene

Area of Science:

• Supramolecular Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Development of selective chemosensors for hazardous anions and cations is crucial for environmental safety.
• Calix[4]arene scaffolds offer a versatile platform for designing host molecules with specific binding properties.

Purpose of the Study:

• To synthesize and characterize a new quinoline-amide calix[4]arene receptor.
• To investigate the receptor's sensing capabilities for various hazardous anions and metal ions.
• To evaluate the selectivity and sensitivity of the receptor for target analytes.

Main Methods:

• Synthesis of the quinoline-amide calix[4]arene receptor.
• UV-vis and fluorescence spectroscopy for sensing studies.
• Proton Nuclear Magnetic Resonance (NMR) spectroscopy for anion-binding investigations.

Main Results:

• The synthesized receptor demonstrated selective sensing for dichromate (Cr₂O₇^2-) and mercury (Hg²⁺) ions.
• Higher association constants were observed for dichromate compared to mercury ions.
• Fluorescence measurements indicated high selectivity for dichromate over other tested anions and cations, with a low limit of detection (7.36×10^-6 moldm^-3).
• Proton NMR studies confirmed strong interactions between the dichromate anion and the receptor's NH and CH groups, attributed to hydrogen bonding.

Conclusions:

• The quinoline-amide calix[4]arene receptor is a highly selective and sensitive sensor for dichromate ions.
• The receptor's design, incorporating hydrogen-bond donor groups, enhances anion binding affinity.
• This receptor shows significant potential for the selective detection of Cr(VI) in environmental samples.