Redox-Active M8 L6 Cubic Hosts with Tetraphenylethylene Faces Encapsulate Organic Dyes for Light-Driven H2 Production.

Abstract

The design of artificial systems that mimic highly evolved and finely tuned natural enzymes is a promising subject of intensive research. The assembly of O-symmetric cubic structures with an Fe8 L6 formula was reported through the direct combination of a C4 -symmetric tetraphenylethylene-based ligand with a C3 -symmetric tris(bipyridine)iron node. The robust metal-organic cubes are rich in π-electron density and provide favorable interactions with planar polycyclic aromatic hydrocarbons. Within the confined space of the host, the aromatic hydrocarbons molecules are forced closer to the redox active host, and the photoinduced electron transfer (PET) is modified into a pseudo-intramolecular pathway. These iron vertices within the cubes exhibit suitable redox potential for electrochemical reduction of protons and the well-modified PET is further tailored to create artificial systems for light-driven hydrogen evolution from water through the encapsulation of fluorescein dyes. Control experiments based on a mononuclear compound resembling the iron corner of the octahedron suggest an enzymatic dynamic behavior. The new, well-elucidated reaction pathways and the increased molarity of the reaction within the confined space render these supramolecular systems superior to other relevant systems.