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.