Aggregation-induced emission from optically active X-shaped molecules based on planar chiral [2.2]paracyclophane

Area of Science:

• Organic chemistry
• Materials science
• Photophysics

Background:

• Optically active molecules are crucial for developing advanced optical materials.
• Achieving strong circularly polarized luminescence (CPL) and aggregation-induced emission (AIE) simultaneously remains a challenge.
• Incorporating rigid chiral units like paracyclophanes can influence molecular packing and optical properties.

Purpose of the Study:

• To synthesize a novel π-stacked molecule combining planar chiral [2.2]paracyclophane and o-carborane units.
• To investigate the molecule's photophysical properties, including aggregation-induced emission (AIE) and circularly polarized luminescence (CPL).
• To explore the potential of this molecule in solid-state applications for enhanced optical performance.

Main Methods:

• Synthesis of a π-stacked molecule featuring planar chiral [2.2]paracyclophane and o-carborane moieties.
• Photophysical characterization in solution and aggregated states, including emission spectroscopy.
• Investigation of CPL properties in mixed solvents and solid-state matrices (PMMA).
• Computational studies using time-dependent density functional theory (TD-DFT).

Main Results:

• The synthesized molecule displayed strong emission in the aggregated state (H2O/THF mixture) and solid-state (PMMA).
• Weak CPL was observed in the aggregated state due to random intermolecular orientation.
• Clear CPL was achieved in a PMMA film containing 1 wt% of the molecule.
• TD-DFT calculations successfully reproduced the observed circular dichroism and CPL properties.

Conclusions:

• The novel molecule successfully integrates AIE and CPL properties.
• Solid-state incorporation, particularly in a PMMA matrix, enhances CPL observation.
• The findings provide a pathway for designing advanced chiral luminescent materials.