Aggregation-induced emission rotors: rational design and tunable stimuli response

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Aggregation-induced emission (AIE) materials exhibit enhanced luminescence upon aggregation.
• Tuning the stimuli response of AIE materials is crucial for advanced applications.
• Understanding the AIE mechanism, particularly the restriction of intramolecular rotations (RIR), is key for rational design.

Purpose of the Study:

• To develop a novel molecular design strategy for tuning the stimuli response of AIE materials.
• To synthesize and characterize new AIE-active molecules (AIE rotors) with varying numbers of tetraphenylethene (TPE) moieties.
• To investigate the relationship between molecular structure, intramolecular rotation, and sensitivity to environmental stimuli like viscosity and temperature.

Main Methods:

• Covalent linkage of different numbers of tetraphenylethene (TPE) units to create AIE rotors.
• Systematic variation of molecular size and the number of rotatable phenyl rings.
• Experimental characterization of photophysical properties, including luminescence, viscosity sensitivity, and temperature response.
• Analysis of structure-property relationships to elucidate the AIE mechanism.

Main Results:

• A series of novel AIE-active molecules (AIE rotors) were successfully synthesized.
• Increasing the number of rotatable phenyl rings significantly enhanced the sensitivity of AIE rotors to viscosity and temperature.
• Despite increased molecular size, performance improvements were moderate due to increased rotational barriers, offering insight into the RIR mechanism.
• The largest AIE rotor exhibited the highest viscosity sensitivity, with a viscosity factor reaching 0.98.

Conclusions:

• A rational molecular design strategy was established to tune the stimuli response of AIE materials.
• The study provides deeper insights into the AIE mechanism, emphasizing the role of restricted intramolecular rotations.
• The developed AIE rotors demonstrate potential for applications requiring high sensitivity to viscosity and temperature changes.