High-Pressure Spectroscopic Probing of Aggregation-Dependent Luminescence in Tetraphenylethylene: Deciphering Intra-...

Area of Science:

• Materials Science
• Photophysics
• Supramolecular Chemistry

Background:

• Tetraphenylethylene (TPE) is a key aggregation-induced emission luminogen (AIEgen).
• Understanding TPE's response to external stimuli like pressure is crucial for designing advanced materials.
• High-pressure studies reveal complex photophysical behaviors influenced by molecular interactions.

Purpose of the Study:

• To systematically investigate the emission and conformational evolution of TPE under high pressure.
• To elucidate the role of pressure-transmitting media (PTMs) on TPE's photoluminescence.
• To establish correlations between molecular dynamics and optoelectronic responses.

Main Methods:

• High-pressure experimental investigations.
• Systematic photoluminescence spectroscopy.
• Utilizing argon and water as pressure-transmitting media.

Main Results:

• Fluorescence quenching below 1.4 GPa in argon due to altered hydrogen bonding and nonradiative decay.
• An 8-fold luminescence amplification between 1.4 and 4.9 GPa driven by restricted intramolecular rotation (RIR).
• Molecular planarization at 4.9 GPa leading to red-shifted fluorescence and quenching.
• Significant alterations in pressure-induced transitions when using water as a PTM, attributed to hydrogen-bonding networks.
• Intermolecular π-π interactions and π-orbital overlap become dominant quenching factors above 12 GPa.

Conclusions:

• Pressure-dependent photoluminescence of TPE is governed by a balance of intramolecular and intermolecular interactions.
• The choice of PTM critically affects TPE's high-pressure behavior by modulating hydrogen-bonding networks.
• These findings resolve contradictions in previous studies and offer a framework for designing stimuli-responsive AIE materials.