Substrate and product binding inside a stimuli-responsive coordination cage acting as a singlet oxygen photosensitizer. Issue 27 (26th June 2020) - Pullen, Sonja
Abstract : Multiple functionalities of an acridone-based metallosupramolecular assembly: photosensitization of singlet oxygen, allosteric activation as host and encapsulation of the substrate and product of a hetero-Diels-Alder reaction. Abstract : An acridone-based, interpenetrated double cage [3BF4 Pd4 L8 ] acts as a photosensitizer for generating singlet oxygen which adds to 1, 3-cyclohexadiene in a [2+4] hetero-Diels-Alder reaction to form 2, 3-dioxabicyclo[2.2.2]oct-5-ene. Photocatalytic activity was exclusively observed for the assembled cage, whereas the free organic ligand L decomposes upon irradiation. While cage [3BF4 Pd4 L8 ] does not accept any organic guests, NMR, MS and single crystal X-ray results reveal that both substrate and product are readily encapsulated in the central pocket of its chloride-activated form [2Cl@Pd4 L8 ] . The system combines multiple functions (photosensitization, allosteric activation and guest uptake) within a structurally complex, mechanically-bound self-assembly built up from a simple and readily accessible ligand.