From Molecule to Aggregate: Understanding AIE through Multiscale Experimental and Computational Techniques.

Area of Science:

• Materials Science
• Biomedicine
• Physical Chemistry

Background:

• Aggregation-induced emission (AIE) is a crucial phenomenon with broad applications.
• The precise mechanism driving AIE in molecules remains incompletely understood.
• Understanding AIE determinants is key for designing advanced functional materials.

Purpose of the Study:

• To elucidate the fundamental mechanisms governing aggregation-induced emission (AIE).
• To identify the key molecular and aggregate properties that dictate AIE activity.
• To provide design principles for novel AIE-active materials.

Main Methods:

• Synthesis of four organic molecules with D-π-A-D architecture.
• Computational modeling including quantum mechanics (QM) and molecular dynamics (MD) simulations.
• Symmetry-adapted perturbation theory (SAPT) calculations to analyze intermolecular interactions.

Main Results:

• A clear correlation was found between AIE activity and aggregate type (J-type vs. H-type).
• AIE-active molecules form J-type aggregates, enhancing S₁ state emission.
• AIE-inactive molecules form H-type aggregates, restricting S₁ state emission.
• Molecules were observed to localize within lipid droplets.

Conclusions:

• The type of aggregate formed is a critical determinant of AIE activity.
• J-type aggregation enhances emission, while H-type aggregation quenches it.
• Findings offer insights for designing targeted AIE materials for sensing and imaging.