Fluoride ion sensing by an anion-π interaction.

Area of Science:

• Supramolecular Chemistry
• Chemical Sensing
• Materials Science

Background:

• Fluoride ion detection is crucial in environmental and biological monitoring.
• Colorimetric sensors offer a simple and rapid method for ion detection.
• Naphthalene diimide (NDI) derivatives are known for their electron-deficient properties.

Purpose of the Study:

• To report the discovery of a novel anion-π and charge/electron transfer (CT/ET) supramolecular interaction.
• To develop a colorimetric sensor for fluoride ions using NDI receptors.
• To enhance the selectivity and sensitivity of NDI-based fluoride sensing.

Main Methods:

• Investigated supramolecular interactions between fluoride ions and naphthalene diimide (NDI) receptors.
• Utilized charge/electron transfer (CT/ET) mechanisms for sensing.
• Synthesized preorganized NDI units using folded linkers for improved sensor performance.
• Employed UV-Vis spectroscopy to monitor color changes associated with fluoride binding.

Main Results:

• Discovered a unique anion-π and CT/ET interaction between fluoride ions and colorless NDI.
• Observed distinct color changes (orange and pink) upon sequential reduction of NDI by fluoride ions.
• Demonstrated that preorganized NDI receptors exhibit significantly enhanced selectivity and sensitivity for fluoride ions.
• Achieved fluoride detection at nanomolar (nM) concentrations in DMSO/H(2)O solutions.

Conclusions:

• NDI receptors can function as effective colorimetric sensors for fluoride ions through ET events.
• Preorganization of NDI units dramatically improves sensor performance, enabling sensitive and selective detection.
• This work presents a promising approach for developing advanced chemosensors for critical anion detection.