Light-driven Hydrogen Evolution from Water by a Tripodal Silane Based Co^II₆L¹₈ Octahedral Cage

The octahedral cage assembly [Co^II₆L¹₈Cl₆(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.