A diarylethene cocrystal that converts light into mechanical work.

Area of Science:

• Materials Science
• Crystallography
• Photochemistry

Background:

• Photochromic materials change color upon light exposure.
• Molecular crystals offer unique mechanical properties.
• Diarylethene derivatives are known for their photochromic behavior.

Purpose of the Study:

• To investigate the photomechanical effect of a novel diarylethene-perfluoronaphthalene cocrystal.
• To characterize the reversible bending motion and its underlying mechanism.
• To explore potential applications of this material in molecular actuators.

Main Methods:

• Synthesis and characterization of the 1,2-bis(2-methyl-5-(1-naphthyl)-3-thienyl)perfluorocyclopentene (1o) and perfluoronaphthalene (FN) cocrystal.
• In situ X-ray crystallographic analysis to study crystal deformation.
• Mechanical testing of molecular crystal cantilevers.
• Low-temperature dynamic measurements of bending motion.

Main Results:

• The 1o·FN cocrystal exhibits reversible bending upon alternate UV and visible light irradiation, repeatable over 250 cycles.
• Crystal deformation is attributed to b-axis elongation caused by diarylethene photocyclization.
• Bending motion occurs even at 4.7 K with anisotropic expansion on the microsecond timescale.
• Molecular crystal cantilevers can lift objects 200-600 times their weight.
• Generated stress reaches 44 MPa, comparable to piezoelectric materials.

Conclusions:

• The diarylethene-perfluoronaphthalene cocrystal demonstrates significant photomechanical properties.
• The material exhibits efficient and repeatable light-induced bending and mechanical work.
• This research opens avenues for developing advanced molecular machines and actuators.