Highly Twisted Azobenzene Ligand Causes Crystals to Continuously Roll in Sunlight

Direct conversion of solar energy to mechanical work promises higher efficiency than multistep processes, adding a key tool to the arsenal of energy solutions necessary for our global future. The ideal photomechanical material would convert sunlight into mechanical motion rapidly, without attrition, and proportionally to the stimulus. We describe crystals of a tetrahedral isocyanoazobenzene-copper complex that roll continuously when irradiated with broad spectrum white light, including sunlight. The rolling results from bending and straightening of the crystal due to blue light-driven isomerization of a highly twisted azobenzene ligand. These findings introduce geometrically constrained crystal packing as a strategy for manipulating the electronic properties of chromophores. Furthermore, the continuous, solar-driven motion of the crystals demonstrates direct conversion of solar energy to continuous physical motion using easily accessed molecular systems.

Automated summary

The direct conversion of solar energy to mechanical work is a more efficient energy solution for the future. Researchers have discovered a new crystal material that can continuously roll under sunlight, driven by blue-light reactions. This finding introduces a new strategy for manipulating the electronic properties of chromophores and demonstrates the ability to convert solar energy to continuous physical motion using easily accessible molecular systems.