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 (Pd2L2) 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 (W10O324-) can template the dominant formation of the Pd2L2 host. Guest-adaptive conformational changes and induced-fit cavity deformation of the Pd2L2 host have been clearly observed in the crystal structures. Moreover, the installation of the electron-rich W10O324- cluster within the cationic redox-active host (W10O32 subset of Pd2L2) 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.

Automated summary

The adaptive self-assembly and host-guest catalysis of a new water-soluble organo-palladium host are reported. The host undergoes conformational changes upon guest binding, allowing for efficient and selective catalysis.