Imidazole-based solid-state fluorescence switch: Stimuli-responsive emission, mechanochromism and acidochromism

Area of Science:

• Materials Science
• Organic Chemistry
• Supramolecular Chemistry

Background:

• Imidazole-based compounds are explored for unique optical properties.
• Aggregation-induced emission (AIE) probes offer enhanced fluorescence in the solid state.
• Mechanochromism and acidochromism are desirable for advanced sensor applications.

Purpose of the Study:

• To synthesize and characterize a novel imidazole-based molecular probe (Ph-ISO).
• To investigate the solid-state fluorescence, aggregation-induced emission (AIE), mechanochromism, and acidochromism of Ph-ISO.
• To explore the potential applications of Ph-ISO in rewritable papers and pH monitoring.

Main Methods:

• Synthesis and characterization of the (E)-2-(5,5-dimethyl-3-(4-(1,4,5-triphenyl-1H-imidazole-2-yl)styryl)cyclohex-2-en-1-ylidene)malononitrile (Ph-ISO) probe.
• Solid-state fluorescence spectroscopy to study emission properties.
• Mechanical stress (grinding) and acid treatment to induce changes in optical properties.
• Single crystal X-ray analysis to elucidate intermolecular interactions and conformational changes.

Main Results:

• Ph-ISO exhibits intense solid-state fluorescence due to aggregation-induced emission (AIE).
• The probe displays reversible mechanochromism, shifting emission upon grinding (crystalline to amorphous state).
• Ph-ISO shows switchable acidochromism, indicating potential for pH sensing.
• Solid-state emission is attributed to intermolecular C-H---N and C-H---π interactions in a twisted conformation.

Conclusions:

• Ph-ISO is a versatile molecular probe with AIE, reversible mechanochromism, and acidochromism.
• The observed properties are linked to conformational changes and intermolecular interactions in the solid state.
• Ph-ISO holds promise for applications in rewritable materials and environmental/biological pH monitoring.