DHPA-Containing Cobalt-Based Redox Metal-Organic Cyclohelicates as Enzymatic Molecular Flasks for Light-Driven H2 Production.

The supramolecular assembly of predesigned organic and inorganic building blocks is an excellent tool for constructing well-defined nanosized molecular cavities that catalyse specific chemical transformations. By incorporating a reduced nicotinamide adenine dinucleotide (NADH) mimic within the ligand backbone, a redox-active cobalt-based macrocycle was developed as a redox vehicle for the construction of an artificial photosynthesis (AP) system. The cyclohelicate can encapsulate fluorescein within its cavity for light-driven H2 evolution, with the turnover number (TON) and turnover frequency (TOF) reaching 400 and 100 moles H2 per mole redox catalyst per hour, respectively. Control experiments demonstrated that the reactions were potentially occurred within the cavity of the cyclohelicates which were inhibited in the presence of adenosine triphosphate (ATP), and the redox-active NADH mimic dihydropyridine amido moieties within the ligands played an important role in photocatalytic proton reduction process.