Reversible Photochromic Coordination Polymer by Phototriggered Subtle Molecular Conformation Variations

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Photochromic materials change structure upon light exposure, crucial for many applications.
• Molecule stacking in coordination polymers (CPs) often hinders photochromic efficiency and response time.

Purpose of the Study:

• To develop a CP with enhanced photochromic properties overcoming space-confinement limitations.
• To investigate the mechanism behind the fast, reversible photochromism in the new CP.

Main Methods:

• Synthesis of a 3-fold-interpenetrating network CP (CIT-Z) using a specific ligand and CuI.
• Analysis of single-crystal structures in different color states.
• Time-dependent density functional theory (TD-DFT) calculations and control experiments.

Main Results:

• CIT-Z exhibits fast reversible photochromism, changing from pale yellow to reddish brown under UV light and returning within 10s with green light.
• The photochromic behavior is attributed to a ligand-to-metal charge-transfer process triggered by molecular conformation changes.
• The material demonstrates high thermal and chemical stability.

Conclusions:

• The developed CP (CIT-Z) offers a promising solution for efficient, reversible photochromic materials.
• Its stability and tunable properties open avenues for applications in anticounterfeiting and optical data storage.