Annulated oxazolium salts as anion-π⁺ interaction-enabled solid-state room-temperature phosphorescent materials

Area of Science:

• Materials Science
• Photophysics
• Organic Chemistry

Background:

• Ionic luminescent materials offer tunable photophysical properties.
• Modulating these properties often requires complex structural modifications.
• Counter-anion exchange presents a simpler alternative for property tuning.

Purpose of the Study:

• To investigate the effect of counter-anion exchange on the photophysical properties of annulated oxazolium salts.
• To demonstrate the conversion of fluorescence to room-temperature phosphorescence via anion exchange.

Main Methods:

• Synthesis of fluorescent annulated oxazolium salts.
• Counter-anion exchange using hexafluorophosphate (PF6-) and iodide (I-) salts.
• Characterization of photophysical properties (fluorescence and phosphorescence).

Main Results:

• Annulated oxazolium salts exhibiting fluorescence were successfully synthesized.
• Exchange of the hexafluorophosphate (PF6-) anion with iodide (I-) resulted in a switch from fluorescence to room-temperature phosphorescence.
• The anion exchange process did not require structural modification of the oxazolium core.

Conclusions:

• Counter-anion exchange is an effective strategy for tuning the luminescence of ionic materials.
• This method enables the facile conversion of fluorescent organic materials to phosphorescent ones.
• The findings open avenues for designing novel luminescent materials with tailored properties.