Biomimetic systems trigger a benzothiazole based molecular switch to 'turn on' fluorescence

Area of Science:

• Supramolecular Chemistry
• Organic Chemistry
• Biophysical Chemistry

Background:

• Schiff bases offer simple synthesis and diverse biochemical applications.
• Molecular switches are crucial for detecting chemical and biological processes.
• Designing Schiff bases as molecular switches for biomimetic environments is of significant interest.

Purpose of the Study:

• To demonstrate a strategically designed benzothiazole Schiff base (CBMDP) functioning as a fluorescent molecular switch.
• To investigate the fluorescence modulation of CBMDP in aqueous and biomimetic environments.
• To explore the structural and environmental factors influencing CBMDP's fluorescence.

Main Methods:

• Utilized electronic absorption, steady-state, and time-resolved fluorescence spectroscopy.
• Employed DFT-based quantum chemical calculations.
• Investigated spectral behavior in various solvent mixtures (water-dioxane, water-methanol) and micellar/liposome media.

Main Results:

• In organic solvents, CBMDP exhibits high fluorescence (enol-imine, N form).
• In aqueous media, CBMDP transforms into a weakly fluorescent hydrated species (H form).
• Interaction with micellar or liposome environments restores CBMDP to its highly fluorescent N form, indicating molecular flipping.

Conclusions:

• The designed Schiff base CBMDP acts as a "turn off-turn on" fluorescent molecular switch.
• Micropolarity and structural stability against hydrolysis are key to CBMDP's fluorescence restoration.
• CBMDP shows promise for applications in biochemical sensing.