Light-driven Hydrogen Evolution from Water by a Tripodal Silane Based CoII6L18 Octahedral Cage.

The octahedral cage assembly [CoII6L18Cl6(H2O)6]Cl6 has been synthesized in a single-step reaction by using a polypyridyl-functionalized tripodal silane ligand. The electrochemical behavior of the cage in water exhibits the pH dependence of potential as well as catalytic current indicating the possible involvement of proton-coupled electron transfer in H2 evolution. Electrocatalytic hydrogen evolution from an aqueous buffered solution gave a turnover frequency of 16 h-1. Further, this cage assembly has been explored as a photocatalyst (blue light irradiation λ 469 nm) for the evolution of H2 from water in the presence of Ru(bpy)32+ as a photosensitizer and ascorbic acid as a sacrificial electron donor. This catalytic reaction is found to be pseudo first order with a turnover frequency of 20.50 h-1.