Photoinduced peeling of molecular crystals.

Block-like microcrystals composed of cis-dimethyl-2(3-(anthracen-9-yl)allylidene)malonate are grown from aqueous surfactant solutions. A pulse of 405 nm light converts a fraction of molecules to the trans isomer, creating an amorphous mixed layer that peels off the parent crystal. This photoinduced delamination can be repeated multiple times on the same block.

Photomechanically Induced Magnetic Field Response by Controlling Molecular Orientation in 9-Methylanthracene Microcrystals.

A surfactant-assisted seeded-growth method is used to form single-crystal platelets composed of 9-methylanthracene with two different internal molecular orientations. The more stable form exhibits a photoinduced twisting, as observed previously for 9-methylanthracene microribbons grown by the floating drop method. However, the newly discovered elongated hexagonal platelets undergo a photoinduced rolling-up and unrolling. The ability of the rolled-up cylindrical shape to trap superparamagnetic nanoparticles enables it to be carried along in a magnetic field gradient. The new photoinduced shape change, made possible by a novel surfactant-assisted crystal growth method, opens up the possibility of using light to modulate the crystal translational motion.

Highly branched photomechanical crystals.

When a suspension of the tert-butyl ester of 4-fluoroanthracene-9-carboxylic acid (4F9AC) was slowly hydrolyzed, highly branched photomechanical microcrystals of 4F9AC were grown. Exposure to UV light caused the branches to undergo a reversible sweeping motion that could be used to move and concentrate silica microspheres on a surface.