Light-Triggered Guest Uptake and Release by a Photochromic Coordination Cage

摘要

The selective encapsulation of guest compounds by discrete, molecular-scale cages has been applied to various separation and purification tasks, the capturing of hazardous chemicals, the stabilization of reactive intermediates, and the realization of sensing systems. A prerequisite for all these applications is strong binding between the host and the particular guest compound. Certain other applications, however, necessitate dynamic control over the strength of the host-guest interaction. In particular, systems designed for the uptake, delivery, and release of cargo (such as drugs or site-specific markers for bioimaging purposes) require temporal and spatial control over the localization of the guest molecules either inside or outside of the host cavity. Furthermore, the action of such control mechanisms may help to overcome one central limitation imposed on the field of supramolecular catalysis in confined cavities, that is, product inhibition. A desirable strategy would be one in which the cage itself is enabled to control the presence or absence of guests inside its interior, most preferably triggered by a waste-free external stimulus, such as light.