Photochemical investigation of cyanoazobenzene derivatives as components of artificial supramolecular pumps.

Among the plethora of photochromes reported so far, azobenzene has been proven to be the most suitable photoswitch for molecular systems and materials, due to its highly efficient and clean E-Z photoisomerization. Here we report two ammonium-based molecular axles bearing one or two p-cyanoazobenzene units at the extremities, able to form pseudorotaxanes with a crown ether macrocycle. The photochemistry of these compounds was studied in the isolated forms and in the pseudorotaxanes, showing that the functionalization speeds up the threading process without affecting the photochemical properties of the system. These results suggest that the investigated pseudorotaxanes can form the basis of new prototypes of artificial molecular-level pumps.