Photorelease of an Organic Molecule in Solution: Light-Triggered Blockage of a Hydrogen-Bonding Receptor Site

摘要

The selective recognition of a guest by a molecular host is a fundamental process whose understanding has led to the design of systems that are capable of controlled associative/dissociative behavior.[1] Such systems rely on an external physical or chemical stimulus to modulate reversible intermolecular forces that are responsible for the association of two or more species, and they are ubiquitous to all living organisms, wherein they play a vital role in complex signal-transmission, regulation, and amplification processes. There are now several examples of receptor molecules that contain photoresponsive units for which the strength of a binding interaction with a particular guest species in solution can be controlled by light.[2] The vast majority of these receptors rely on a photochromic auxiliary to impart a light-induced structural modification of a crown-ether-like cavity. Although the flexibility of the crown ether units facilitates the modulation of their binding properties, such systems have so far been focused on the binding of metal ions, whereas reports of photoresponsive receptors that bind organic species through multiple hydrogen-bonding interactions are rare.[2e], [3] Herein, we demonstrate how light controls the binding affinity of a hydrogen-bonding receptor towards a neutral organic molecule to such an extent that the bound guest (barbital) is effectively released upon photoirradiation.