Long-living optical gain induced by solvent viscosity in a push-pull molecule.

Area of Science:

• Photonic materials science
• Physical chemistry
• Molecular spectroscopy

Background:

• Aggregation-induced emission (AIE) is a phenomenon where molecules exhibit enhanced fluorescence in aggregated states.
• Twisted intramolecular charge transfer (TICT) is a key photophysical mechanism influencing molecular emission properties.
• Understanding the interplay between molecular structure, environment, and photophysics is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the photophysical properties of a novel push-pull molecule with AIE characteristics.
• To elucidate the role of the twisted intramolecular charge transfer (TICT) mechanism in the molecule's emission.
• To explore the influence of environmental rigidity on TICT and optical gain.

Main Methods:

• Ultrafast pump-probe spectroscopy was employed to study excited-state dynamics.
• Continuum spectroscopy provided insights into spectral features.
• Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations were used for theoretical analysis.
• Experiments were conducted in both viscous and non-viscous environments.

Main Results:

• The study successfully unraveled key features of the TICT mechanism in the new AIE molecule.
• Long-lived optical gain was observed when the TICT mechanism was inhibited.
• Environmental rigidity was identified as a critical factor influencing the observed phenomena.

Conclusions:

• The combination of experimental spectroscopy and theoretical calculations effectively characterizes TICT dynamics.
• Inhibiting TICT can lead to significant optical gain, valuable for photonic applications.
• Molecular design for photonic applications should consider environmental rigidity to control photophysical processes.