Electronic strain effect on Eu(iii) complexes for enhanced circularly polarized luminescence

Area of Science:

• Coordination Chemistry
• Materials Science
• Photophysics

Background:

• Luminescent lanthanide complexes are crucial for various applications, including lighting and sensing.
• Understanding the relationship between ligand structure and luminescence properties is key to designing efficient emitters.
• Chiral ligands can induce unique chiroptical properties in metal complexes.

Purpose of the Study:

• To synthesize and characterize novel luminescent Europium(III) complexes with point-chiral phosphine oxide ligands.
• To investigate the effect of structural and electronic strain on the coordination sphere and luminescence.
• To explore the chiroptical properties of these chiral Eu(III) complexes.

Main Methods:

• Synthesis of Europium(III) complexes: [Eu(hfa)3((R,R)-B2QPO)] and [Eu(hfa)3((R)-B3QPO)].
• Single crystal X-ray crystallography to determine structural details.
• Luminescence spectroscopy (emission quantum yields) and chiroptical spectroscopy (circular dichroism and circularly polarized luminescence).

Main Results:

• The complex [Eu(hfa)3((R,R)-B2QPO)] exhibits strong structural strain in its hexafluoroacetylacetonato (hfa) ligands.
• High emission quantum yields were observed for [Eu(hfa)3((R,R)-B2QPO)] in both solution (55%) and solid (63%) states.
• Chiroptical properties were successfully characterized, with a dissymmetry factor of 0.08 for [Eu(hfa)3((R,R)-B2QPO)].

Conclusions:

• The synthesized chiral Eu(III) complexes demonstrate efficient luminescence comparable to existing bright emitters.
• Structural and electronic strains, particularly ligand-to-metal charge transfer (LMCT), are closely linked to the observed chiroptical phenomena.
• These findings provide valuable insights into the design principles for chiral luminescent materials based on lanthanide complexes.