Halochromic Benzazolo-oxazolidine/Polyoxometalate Supramolecular Materials with Reversible High-Contrast...

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Inorganic Chemistry

Background:

• Stimulus-responsive materials are crucial for advanced applications.
• Polyoxometalates (POMs) offer unique structural and electronic properties.
• Benzazolo-oxazolidine (BOX) derivatives are known for their responsiveness.

Purpose of the Study:

• To synthesize and characterize the first halochromic supramolecular ionic assemblies of BOX derivatives with POMs.
• To investigate the halochromic properties and stability of these novel hybrid materials.
• To explore the potential of these materials in sensing and responsive systems.

Main Methods:

• Synthesis of hybrid materials by combining BOX derivatives with Lindqvist-type POMs ([M6O19]2-, M = Mo, W).
• Structural characterization using single-crystal X-ray diffraction.
• Investigation of solid-state halochromic properties using thin films and exposure to HCl vapor.
• Kinetic studies of color switching and recovery processes.

Main Results:

• Successful formation of three hybrid materials: (3o)2[M6O19] (M = Mo, W) and (3op)2[W6O19]Cl2.
• Demonstrated high-contrast, reversible color switching of (3o)2[M6O19] films upon exposure to and release of HCl vapor.
• Enhanced stability of the protonated BOX cation (3op) within the POM framework due to noncovalent interactions.
• Good cyclability of the hybrid materials over multiple acid vapor trapping-releasing cycles.

Conclusions:

• The developed supramolecular assemblies represent a new class of halochromic materials.
• The interaction with POMs enhances the stability and responsiveness of the BOX derivative.
• These materials show promise for applications in chemical sensing and smart coatings.