Responsive Organic Fluorescent Aggregates Based on Ion-π Interactions Away from Fluorescent Conjugated Groups

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Responsive organic luminescent aggregates are valuable but lack effective molecular design strategies.
• Ion-π interactions can tune luminescent properties, but current designs focus on strong interactions at conjugated groups.
• A need exists for flexible molecular designs that control ion-π interactions for responsive luminescence.

Purpose of the Study:

• To introduce flexible alkoxy chain spacers to decouple fluorescent groups from ion-π interaction sites.
• To investigate how varying ion-π interaction strength influences fluorescence performance in solid-state materials.
• To demonstrate a new class of responsive organic luminescent solid-state materials.

Main Methods:

• Molecular design incorporating flexible alkoxy chain spacers between fluorescent units and ion-π interaction sites.
• Synthesis and characterization of bromine ion-based and hexafluorophosphate ion-based molecules.
• Evaluation of fluorescence quantum yields in crystalline and amorphous states under external stimuli.

Main Results:

• Bromine ion-based molecules with strong ion-π interactions showed high, stable fluorescence quantum yields in both crystal and amorphous forms.
• Hexafluorophosphate ion-based molecules with weak ion-π interactions exhibited high quantum yields in crystals but very low yields in amorphous powders.
• The study demonstrated variable fluorescence intensities under external stimuli, correlating with ion-π interaction strength.

Conclusions:

• Flexible alkoxy chain spacers effectively modulate ion-π interactions and subsequent fluorescence properties.
• This strategy enables the design of responsive organic luminescent solid-state materials with tunable characteristics.
• The findings present a novel approach for developing advanced luminescent materials for diverse applications.