Molecular crystal microribbons formed by 9-anthracenecarboxylic acid (9AC) show reversible twisting by irradiating and turning-off 440nm light, which originates from a reversible [4+4] photodimerization.  For applications of these microribbons, for example as photomechanical actuators, ways to connect molecular crystals to external objects need to be developed without sacrificing the reversible photomechanical properties of these molecular crystals.  A simple strategy for this purpose is to coat thin gold layer on the surface of the molecular crystal and use this gold layer as an interface for attaching external molecules.  Molecular crystals are formed by slowly evaporating a solvent (ethyl acetate) of 1.9 mg/ml solution on a clean water surface in a Petri dish.  These microribbons are collected on an Anodisc filter and dried under vacuum.  A gold layer of 10 nm thickness was deposited using e-beam evaporation, and the supporting Anodisc filter was dissolved in a 50% phosphoric acid solution. With a gold layer on the surface, the 9AC molecular crystals maintain their reversible twisting behavior.  It is expected that external molecules with thiol groups can be immobilized onto the surface of these gold-coated microribbons and provide them with various functionalities.  The coating of the microribbons with a magnetic metal like Ni will also be described, so that the ribbons can be moved using an external magnetic field.

Reversible photoinduced twisting of metal-coated molecular crystal microribbons

243rd National Meeting (2012)

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