Electronic decoupling approach to quantitative photoswitching in linear multiazobenzene architectures

Area of Science:

• Organic Chemistry
• Materials Science
• Photochemistry

Background:

• Azobenzene derivatives are key photochromic materials.
• Controlling photoswitching efficiency in multiazobenzene systems is challenging.
• Existing rigid linear multiazobenzene constructs often suffer from limited photoswitching performance.

Purpose of the Study:

• To develop a strategy for optimizing photoswitching efficiency in rigid, linear multiazobenzene constructs.
• To investigate the impact of dihedral angles between azobenzene moieties on photochromic properties.
• To enable efficient light energy transduction into motion using molecular architectures.

Main Methods:

• Synthesis of four bisazobenzene compounds with varying dihedral angles and three reference compounds.
• Experimental study of photoswitching behavior (photoisomerization and thermal isomerization).
• Theoretical analysis including quantum chemical calculations and electrochemical studies.

Main Results:

• Increased dihedral angles lead to decreased electronic conjugation and improved photochromic characteristics.
• Electronic decoupling enables independent operation of azobenzene units, achieving up to 97% E → Z photoisomerization.
• Absorption spectra separation and independent thermal Z → E isomerization were observed with increasing decoupling.
• Theoretical calculations provided mechanistic insights into thermal isomerization pathways.

Conclusions:

• Introducing large dihedral angles between azobenzene units is an effective strategy to optimize photoswitching efficiency.
• Electronic decoupling is crucial for achieving quantitative photoswitching in multiazobenzene systems.
• This approach provides a foundation for designing rigid rod architectures with highly efficient photoswitching properties for light-energy transduction.