Harnessing Solar Energy, Extending Storage, and Accelerated Release in "Twisted" Negative Photochromic Azo Compounds.

Area of Science:

• Organic Chemistry
• Materials Science
• Photochemistry

Background:

• Molecular Solar Thermal (MOST) energy storage is crucial for renewable energy.
• Azo-based compounds are explored for their photochromic properties.
• Developing efficient and stable MOST materials remains a challenge.

Purpose of the Study:

• To design and synthesize novel twisted (hetero)arylazonaphthalene derivatives for MOST applications.
• To investigate the photochromic behavior, particularly negative photochromism and E-Z isomerization.
• To explore stimuli-responsive isomerization for controlled energy release.

Main Methods:

• Synthesis of twisted (hetero)arylazonaphthalene derivatives.
• Structural characterization using X-ray diffraction (XRD).
• Photochemical studies including E-Z and Z-E isomerization kinetics.
• Evaluation of thermal stability and energy storage capacity (ΔH_iso).
• Fabrication and testing of thin films in a poly(methyl methacrylate) (PMMA) matrix.

Main Results:

• Demonstrated negative photochromism and sunlight-induced E-Z photoisomerization.
• Achieved tunable thermal half-lives (t_1/2) for Z isomers from days to seconds, even in acidic media.
• Exhibited multi-mode activation of Z-E isomerization, including triplet photosensitization.
• PMMA matrix films retained photoswitching behavior and showed sensitivity to pH.
• Quantified energy storage with ΔH_iso up to 35 kJ mol^-1.

Conclusions:

• The geometrical azo-twist is key to negative photochromism.
• These azo derivatives function effectively as MOST materials with tunable charging and discharging.
• The materials demonstrate potential for on-demand energy release and multi-domain applications.
• The developed compounds offer a versatile platform for advanced energy storage solutions.