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Confining molecules to volumes not larger than the molecules themselves can profoundly alter their
chemical properties. Molecular switches1-3 – entities, which can be toggled between two or more forms
upon exposure to external stimuli – often
require conformational freedom to
isomerize, and placing them in confined
spaces typically renders them nonswitchable4
. To preserve the switchability
of these species under confinement, we
encapsulated them in the cavity of a
water-soluble, metal-organic cage that is flexible and can adapt its shape to the conformation of the
bound guest. We show that our “breathable” cage is capable of not only accommodating—and
solubilizing in water—a wide range of structurally diverse guests – it also provides an environment
suitable for the efficient, reversible photoisomerization of molecular switches, including spiropyrans and
azobenzenes. Taking advantage of these findings, we developed two novel time-sensitive information
storage media: a paper, on which writing can be performed using water as the ink, and a gel, which can
be reversibly patterned using light5-6
. Our findings pave the way towards studying a variety of molecular
switching processes in confined environments. |