Achieving Molecular Fluorescent Conversion from Aggregation-Caused Quenching to Aggregation-Induced Emission by...

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Positional isomers are crucial in tuning molecular properties.
• Aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) are key photophysical phenomena.
• Controlling molecular packing is essential for targeted optical properties.

Purpose of the Study:

• Synthesize and characterize positional isomers with varying pyrrolidinyl group positions.
• Investigate the impact of substituent position on fluorescent properties.
• Understand the structure-property relationships governing AIE and ACQ effects.

Main Methods:

• Synthesis of pyrrolidinyl-substituted conjugated isomers.
• Absorption and fluorescence spectroscopy.
• Density functional theory (DFT) calculations.
• Single-crystal X-ray diffraction analysis.

Main Results:

• Two positional isomers, PDB2 (ortho) and PDB4 (para), were synthesized.
• PDB2 displayed aggregation-induced emission (AIE) properties.
• PDB4 exhibited traditional aggregation-caused quenching (ACQ).
• Isomer substituent position influenced molecular twist and packing, leading to varied fluorescence.

Conclusions:

• The position of electron-donating groups significantly alters photophysical behavior.
• Molecular design strategies can control AIE and ACQ phenomena through substituent placement.
• This study provides a pathway for developing novel aggregation-induced emission luminogens.