Fluorescent Multiple-State Emitters Based on Benzonitrile-2-(2'-hydroxyphenyl)benzazoles (HBX)

Area of Science:

• Organic Chemistry
• Photophysics
• Computational Chemistry

Background:

• 2-(2 ahydroxyphenyl)benzazoles (HBX) exhibit excited-state intramolecular proton transfer (ESIPT).
• ESIPT in HBX typically results in quenched fluorescence in solution.
• Boosting fluorescence quantum yield in solution is a significant challenge.

Purpose of the Study:

• To synthesize and characterize novel HBX derivatives.
• To enhance the fluorescent quantum yield of HBX in solution.
• To explore the potential of these compounds as ultrasensitive ratiometric probes.

Main Methods:

• Synthesis of functionalized 2-(2 ahydroxyphenyl)benzazoles.
• Photophysical property measurements in solution.
• Ab initio calculations to understand electronic structure and excited states.

Main Results:

• Novel HBX derivatives functionalized with benzonitrile and ethynyl-triisopropylsilane substituents were synthesized.
• Achieved record high quantum yields for the ESIPT transition, up to 52% in solution.
• Demonstrated strong multiple-state emissive transitions with distinct emission wavelengths.
• Showcased that photophysical properties can be modulated by the heteroatom in HBX.

Conclusions:

• The developed HBX derivatives show significantly improved fluorescence quantum yields in solution.
• The strategic functionalization enables strong multiple-state emission.
• These findings pave the way for developing ultrasensitive ratiometric probes based on HBX.