Difluoroboron Complexes Based on Benzimidazole-Phenolates as Blue Emitters

Area of Science:

• Coordination Chemistry
• Materials Science
• Organic Electronics

Background:

• Four-coordinated boron complexes are synthesized using benzimidazole-phenolate ligands.
• These N,O-donor ligands form complexes with BF3·CH3OH.

Purpose of the Study:

• To synthesize and characterize novel four-coordinated boron complexes.
• To investigate the structure-property relationships influencing their photophysical properties.
• To explore their potential in optoelectronic applications.

Main Methods:

• Synthesis of boron complexes (1-5) from BF3·CH3OH and benzimidazole-phenolate ligands (L1-L5).
• Characterization using NMR (1H, 13C, 11B, 19F), elemental analysis, and single-crystal X-ray diffraction.
• Theoretical calculations using time-dependent density functional theory (TD-DFT).

Main Results:

• Complexes exhibit intense blue emission with notable fluorescence quantum yields (ΦF) in solution and solid states.
• Electron-donating substituents on the phenolate moiety shift emission wavelengths and increase ΦF.
• Incorporation of an aromatic ring on the benzimidazole moiety enhances radiative relaxation.
• Solid-state ΦF values range from 0.18 to 0.57, maintaining or exceeding solution values.
• TD-DFT calculations confirm the tunability of optical bandgaps via ligand substitution.

Conclusions:

• Ligand design offers a pathway to tune the optical properties of boron complexes.
• These complexes show potential for optoelectronic devices due to their strong blue emission and high solid-state fluorescence quantum yields.
• The study establishes a clear structure-property correlation for developing advanced luminescent materials.