Phosphorescence properties of boron β-diketiminate complexes modulated by spiro structures

Area of Science:

• Photochemistry
• Materials Science
• Organic Chemistry

Background:

• Understanding triplet excited states is crucial for organic electronics and photonics.
• Generating triplet states in organic molecules without heavy atoms is challenging due to spin-forbidden intersystem crossing.
• Previous work showed heavy atoms enhance room-temperature phosphorescence in β-diketiminate complexes.

Purpose of the Study:

• To achieve room-temperature phosphorescence in β-diketiminate complexes without relying on heavy atoms.
• To explore the use of twisted donor-acceptor systems and spiro structures for phosphorescence.
• To investigate the role of molecular design in controlling photophysical properties.

Main Methods:

• Synthesis of novel biphenylene-based and diolate-based spiro β-diketiminate boron complexes.
• Photophysical characterization of the synthesized complexes, including emission studies.
• Theoretical calculations (e.g., DFT) to elucidate electronic structures and mechanisms.

Main Results:

• Biphenylene-based spiro complexes exhibited efficient room-temperature phosphorescence.
• Diolate-based spiro complexes showed only weak room-temperature emission.
• Theoretical calculations indicated that interligand charge-transfer states and biphenylene units facilitate intersystem crossing and phosphorescence.

Conclusions:

• Spiro construction of twisted donor-acceptor systems in β-diketiminate boron complexes enables heavy-atom-free room-temperature phosphorescence.
• The electronic properties of the ligands, particularly the biphenylene units, are key to achieving efficient phosphorescence.
• This research opens avenues for designing new phosphorescent materials for various optoelectronic applications.