Intramolecular C-H⋅⋅⋅O Hydrogen-Bonded Solid Emitter as Colorimetric and Fluorometric Cyanide-Selective...

Area of Science:

• Chemical Sensing
• Materials Science
• Organic Chemistry

Background:

• Intramolecular hydrogen bonds (H-bonds) significantly influence the photophysical properties of small molecules.
• Intramolecular charge transfer (ICT) is a key characteristic in designing responsive molecular probes.
• Developing selective and sensitive sensors for toxic analytes like cyanide (CN^-) remains a critical challenge.

Purpose of the Study:

• To design and synthesize a novel indole-indanedione-based small molecule (1Me) for the selective colorimetric and fluorometric detection of cyanide.
• To investigate the role of intramolecular C-H⋅⋅⋅O H-bond and ICT in the sensing mechanism of 1Me.
• To develop a portable and user-friendly cyanide detection method using paper-based test kits.

Main Methods:

• Synthesis of the indole-indanedione-based small molecule, 1Me.
• Spectroscopic analysis (colorimetric and fluorometric) of 1Me in the presence of cyanide ions.
• Investigation of the solid-state fluorescence properties of 1Me.
• Fabrication and testing of paper-based test kits for cyanide detection.

Main Results:

• Compound 1Me exhibits weak fluorescence in solution but strong solid-state yellow fluorescence due to an intramolecular C-H⋅⋅⋅O H-bond inhibiting rotation.
• The addition of cyanide ions to 1Me breaks the H-bond and blocks ICT, leading to distinct colorimetric and fluorometric responses.
• Paper-based test kits incorporating 1Me allow for rapid, naked-eye detection of cyanide in real-time.

Conclusions:

• The study presents a new strategy for designing selective cyanide sensors based on intramolecular H-bonded solid emitters.
• 1Me serves as an effective colorimetric and fluorometric probe for cyanide detection, leveraging its unique solid-state emission properties.
• The developed paper-based test kits offer a practical and convenient platform for on-site cyanide sensing.