Turn-On Mode Fluorescence Switch by Using Negative Photochromic Imidazole Dimer

Area of Science:

• Molecular Chemistry
• Photophysics
• Materials Science

Background:

• Fluorescence imaging of nanostructures requires switchable molecules.
• Photochromic molecules offer reversible, light-triggered fluorescence switching.
• Turn-on mode fluorescence switching remains a limited area of research.

Purpose of the Study:

• To report photoactivatable fluorescence based on negative photochromism.
• To develop reversible turn-on fluorescence switches for nanostructure imaging.

Main Methods:

• Synthesis of a binaphthyl-bridged imidazole dimer with naphthalimide units.
• Investigation of negative photochromism and fluorescence switching properties.
• Analysis of Förster resonance energy transfer (FRET) for fluorescence quenching and enhancement.

Main Results:

• The molecule exhibits negative photochromism with a blue-shifted absorption spectrum post-irradiation.
• Initial isomer shows efficient fluorescence quenching (Φ_fluo. = 0.01) via FRET.
• Transient isomer displays significantly enhanced fluorescence quantum yield (Φ_fluo. = 0.75).
• Thermal back reaction leads to a decrease in fluorescence intensity.

Conclusions:

• The developed negative photochromic molecules are suitable for turn-on mode fluorescence switches.
• This work provides insights for creating advanced reversible fluorescence switching materials.
• Potential applications in fluorescence imaging and sensing are suggested.