Strategy to enhance solid-state fluorescence and aggregation-induced emission enhancement effect in pyrimidine boron...

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Pyrimidine derivatives are important in various chemical applications.
• Boron complexes offer tunable electronic and photophysical properties.
• Intramolecular rotation and aggregation-induced emission (AIE) are key factors in fluorescence.

Purpose of the Study:

• To synthesize pyrimidine-based monoboron complexes with different boron substituents (BF2 and BPh2).
• To investigate the impact of substituents on solution and solid-state fluorescence properties.
• To explore the relationship between intramolecular rotation, AIE, and fluorescence behavior.

Main Methods:

• Synthesis of pyrimidine-based monoboron complexes.
• Spectroscopic analysis of fluorescence properties in solution and solid-state.
• Investigation of aggregation-induced emission (AIE) effects.
• Evaluation of solvatochromism in fluorescence spectra.

Main Results:

• Non-, trifluoromethyl-, and cyano-substituted complexes showed negligible solution fluorescence due to unrestricted C-Ar rotation.
• Methoxy- and dimethylamino-substituted analogues exhibited restricted rotation and strong solution fluorescence.
• Non-, trifluoromethyl-, and cyano-substituted derivatives displayed significant AIE.
• Dimethylamino-substituted derivatives showed solvatochromism.
• BPh2 complexes demonstrated enhanced solid-state fluorescence quantum yields compared to BF2 analogues.

Conclusions:

• The electronic nature of substituents on pyrimidine-based monoboron complexes significantly influences their photophysical properties.
• Restricting intramolecular rotation is crucial for achieving strong fluorescence in solution.
• AIE is prominent in derivatives with unrestricted rotation.
• BPh2 substitution offers advantages for solid-state fluorescence applications.