Solvent-driven luminescence modulation/switching in an iridium(iii) complex containing an aldehyde group

Area of Science:

• Organometallic Chemistry
• Photophysics
• Materials Science

Background:

• Iridium complexes are widely studied for their photoluminescent properties.
• Tuning luminescence through structural modifications and external stimuli is crucial for advanced applications.
• Solvent-dependent structural changes can significantly impact solid-state emission characteristics.

Purpose of the Study:

• To synthesize a novel iridium complex, [Ir(dfppy)2(phca)]PF6 (1), featuring an aldehyde group in the 1,10-phenanthroline-4-carbaldehyde (phca) ligand.
• To investigate the solvent-driven modulation and switching of luminescence in complex 1.
• To explore the relationship between solvent, solid-state structure, and luminescence properties.

Main Methods:

• Synthesis of the iridium complex [Ir(dfppy)2(phca)]PF6 (1).
• Characterization of luminescence properties in solution (CH3OH, CH2Cl2) and solid states.
• X-ray crystallography to determine solid-state structures (1R in CH2Cl2, 1Y in CHCl3).
• Analysis of structural differences (ππ stacking vs. van der Waals interactions) and their impact on phosphorescence quantum yields (Φ).

Main Results:

• Complex 1 exhibits green emission in CH3OH and orange phosphorescence in CH2Cl2.
• Solid-state structures 1R (red, CH2Cl2) and 1Y (yellow, CHCl3) differ due to crystallization solvent, impacting packing and luminescence.
• 1R shows weak orange phosphorescence (Φ = 3.3%), while 1Y exhibits strong yellow phosphorescence (Φ = 46.6%).
• Reversible phosphorescence switching between orange and yellow is achieved by solvent treatment (CH2Cl2/CHCl3) and mechanical pressing/recrystallization.

Conclusions:

• The synthesized iridium complex demonstrates significant solvent-driven luminescence modulation and switching.
• Solid-state structure, dictated by crystallization solvent and intermolecular interactions, is key to controlling phosphorescence.
• The complex offers potential for developing stimuli-responsive luminescent materials.