Phase-Dependent Reactivity and Host–Guest Behaviors of a Metallo-Macrocycle in Liquid and Solid-State Photosensitized Oxygenation Reactions

The photochemical oxygenation reactions of a host–guest complex, pCp⊂[Ag₂L0]­(SbF₆)₂ (pCp = [2.2]­paracyclophane) have been investigated in solution and in the solid state, using the macrocyclic ligand L0 having four anthracene moieties in the framework. As a result, it was found that the reactivity and host–guest functions show remarkable phase dependence. In solution, the photosensitized oxygenation of all the anthracene moieties of L0 resulted in a fully oxygenated macrocycle [Ag₂L4]­(SbF₆)₂ as the final product, while simultaneously the guest molecule was dissociated from the macrocyclic cavity. On the other hand, in an amorphous solid of pCp⊂[Ag₂L0]­(SbF₆)₂ prepared by decomposing single crystals through the removal of the crystalline solvent, the oxygenated site of L0 was significantly controlled to provide a site-selectively oxygenated inclusion complex, pCp⊂[Ag₂L1]­(SbF₆)₂, possessing a mono-oxygenated C_s-symmetrical macrocyclic skeleton.