Supramolecular Photoinduced Electron Transfer between a Redox-Active Hexanuclear Metal-Organic Cylinder and an Encapsulated Ruthenium(II) Complex

By using redox-active nickel(II) ions as the connect nodes, a hexanuclear metal-organic cylinder (Ni-YL) was achieved through self-assembly with a large cavity and an opening windows capable to accommodate guest molecules. The suitable cavity of Ni-YL provides an opportunity to encapsulate the anionic ruthenium bipyridine derivative [Ru(dcbpy)(3)] (dcbpy=2,2-bipyridine-4,4-dicarboxylic acid) as the photosensitizer for light-driven reactions. The host-guest behavior between Ni-YL and [Ru(dcbpy)(3)] was investigated by mass spectrometry, NMR spectroscopy, and computational studies, revealing an effective binding of the guest [Ru(dcbpy)(3)] within the cavity of Ni-YL. Optical experiments suggested a pseudo-intramolecular photoinduced electron transfer (PET) process between the [Ru(dcbpy)(3)] and the host Ni-YL, leading to an efficient light-driven hydrogen production based on this system. Control experiments with a mononuclear Ni complex as a reference photocatalyst and the inactive [Fe(dcbpy)(3)] as an inhibitor for comparison were also performed to confirm such a supramolecular photocatalysis process.