Weak interactions but potent effect: tunable mechanoluminescence by adjusting intermolecular C-H···π interactions

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photophysics

Background:

• Mechanoluminescence (ML) is a phenomenon where materials emit light upon mechanical stimulation.
• Controlling ML emission colors is crucial for developing advanced optoelectronic devices.
• Designing materials with tunable ML properties remains a significant challenge in materials science.

Purpose of the Study:

• To design and synthesize a novel mechanoluminescent material with tunable emission colors.
• To investigate the relationship between crystal structure, intermolecular interactions, and ML properties.
• To explore the potential of manipulating weak interactions for controlling ML wavelengths.

Main Methods:

• Chemical synthesis of (4-(diphenylamino)phenyl)(4-(diphenylphosphanyl)phenyl)methanone (CDpP).
• Single-crystal X-ray diffraction analysis to determine crystal structures.
• Femtosecond transient emission spectroscopy to study excited-state dynamics.
• Mechanical testing to induce and measure mechanoluminescence.

Main Results:

• Successful synthesis of CDpP, a material exhibiting tunable mechanoluminescence.
• Two distinct ML colors (blue and green) were observed, correlating with different crystalline states.
• C-H···π interactions were identified as the key factor controlling ML color: more interactions led to blue (locally excited state), fewer to green (twisted intramolecular charge transfer state).

Conclusions:

• The study demonstrates a successful strategy for tuning ML emission by manipulating weak intermolecular C-H···π interactions in the crystalline state.
• CDpP serves as a model system for understanding and controlling ML color.
• This work provides a pathway for developing new mechanoluminescent materials with tailored optical properties for various applications.