Polyfunctional Lewis acids: intriguing solid-state structure and selective detection and discrimination of...

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Analytical Chemistry

Background:

• Porphyrin-based compounds are versatile building blocks in supramolecular chemistry.
• Lewis acids are crucial for various chemical transformations and sensing applications.
• Selective detection of nitroaromatic explosives remains a significant challenge in security and environmental monitoring.

Purpose of the Study:

• To synthesize and characterize novel porphyrin-based polyfunctional Lewis acids.
• To investigate the supramolecular assembly and solid-state properties of these compounds.
• To evaluate the potential of these Lewis acids for the selective detection and discrimination of nitroaromatic explosives.

Main Methods:

• Synthesis of three porphyrin-based polyfunctional Lewis acids (compounds 1-3).
• X-ray crystallography to determine the solid-state structures and supramolecular architecture.
• Fluorescence spectroscopy to assess sensing capabilities towards nitroaromatic compounds.
• Density Functional Theory (DFT) calculations to understand electronic structure and Lewis acidity.

Main Results:

• Successful synthesis and structural elucidation of compounds 1-3.
• Compound 3 exhibits unique 3D supramolecular architecture driven by HgCl⋅⋅⋅HgCl interactions.
• Compound 3 demonstrates selective fluorescence quenching in response to picric acid and other nitroaromatic explosives.
• Achieved superior Stern-Volmer quenching constants and detection limits for picric acid compared to existing small-molecular receptors.

Conclusions:

• An electron-deficient polyfunctional Lewis acid has been successfully utilized for selective nitroaromatic explosive detection.
• Compound 3 represents a highly effective small-molecule sensor for picric acid and related explosives.
• The study highlights the potential of porphyrin-based Lewis acids in developing advanced sensing materials.