Light-driven bending of diarylethene mixed crystals

Area of Science:

• Materials Science
• Photochemistry
• Crystallography

Background:

• Photochromic materials change color upon light exposure.
• Molecular shape changes can induce macroscopic material deformation.
• Understanding structure-property relationships is key for designing advanced materials.

Purpose of the Study:

• To investigate the photochromic and light-driven bending properties of mixed crystals.
• To elucidate the relationship between molecular shape changes and macroscopic crystal deformation.
• To explore selective photoisomerization in mixed crystal systems.

Main Methods:

• Synthesis of mixed crystals containing two distinct photochromic molecules.
• Spectroscopic analysis (absorption spectra) to differentiate molecular isomers.
• Selective photoisomerization using specific wavelengths of light (750 nm).
• Microscopy and mechanical testing to observe and quantify crystal bending.

Main Results:

• Mixed crystals of 1,2-bis(2-methyl-5-(p-methoxyphenyl)-3-thienyl)perfluorocyclopentene (1a) and 1,2-bis(5-methyl-2-(p-methoxyphenyl)-4-thiazolyl)perfluorocyclopentene (2a) were successfully prepared.
• Distinct absorption spectra of the closed-ring isomers (1b and 2b) allowed for selective photo-switching.
• Selective photoisomerization of one component in the mixed crystal induced measurable crystal bending.
• The observed macroscopic deformation was directly correlated with the additive local shape changes of individual molecules.

Conclusions:

• The study demonstrates a method for selectively controlling photochromic reactions in mixed crystals.
• Local molecular shape changes are additively linked to macroscopic crystal deformation.
• This work provides insights into designing materials with controlled light-responsive bending capabilities.