New cationic spiropyrans with photoswitchable NIR fluorescence

Area of Science:

• Organic Chemistry
• Materials Science
• Biomedical Applications

Background:

• Photochromic compounds with NIR absorption and fluorescence are crucial for biomedical applications.
• Spiropyrans are a versatile class of photochromic molecules.

Purpose of the Study:

• Synthesize novel spiropyrans with conjugated cationic substituents for NIR absorption and fluorescence.
• Investigate the effect of substituent position on photochromic properties and stability.
• Explore their potential as fluorescent probes for bioimaging.

Main Methods:

• Synthesis of spiropyran derivatives with methoxy groups.
• Spectroscopic analysis (NMR, IR, HRMS).
• X-ray diffraction (XRD) and quantum chemical calculations.
• Photochromism studies in solution and solid state.

Main Results:

• Successfully synthesized spiropyrans with cationic 3H-indolium substituents.
• Observed tunable photochromism (positive/negative) based on substituent position.
• One compound exhibited bidirectional photochromism induced by visible light.
• Photoinduced merocyanine forms showed far-red shifted absorption and NIR fluorescence.

Conclusions:

• The synthesized spiropyrans offer tunable photochromic behavior and NIR fluorescence.
• Structural modifications significantly influence stability and photochromic response.
• These compounds are promising candidates for advanced bioimaging applications.