An Organo-Palladium Host Built from a Dynamic Macrocyclic Ligand: Adaptive Self-Assembly, Induced-Fit Guest Binding, and Catalysis.

Artificial hosts with rich conformational dynamics are attractive to supramolecular chemists due to their adaptive guest-binding properties and enzyme-like catalytic functions. We report here the adaptive self-assembly and host-guest catalysis of a new water-soluble organo-palladium host (Pd 2 L 2 ) built from a pyridinium-bonded macrocyclic ligand (L) and cis-blocked palladium corners (Pd). While the direct self-assembly of L with Pd gives rise to a dynamic mixture of products, both neutral polyaromatic hydrocarbons and an anionic polyoxometalate cluster (W 10 O 32 4- ) can template the dominant formation of the Pd 2 L 2 host. Guest-adaptive conformational changes and induced-fit cavity deformation of the Pd 2 L 2 host have been clearly observed in the crystal structures. Moreover, the installation of the electron-rich W 10 O 32 4- cluster within the cationic redox-active host (W 10 O 32 ⊂Pd 2 L 2 ) facilitates the efficient and selective C-H photooxidation of toluene derivatives to aldehyde products under mild conditions, thus representing an ideal platform for green supramolecular catalysis.