Efficient photo-driven hydrogen evolution by binuclear nickel catalysts of different coordination in noble-metal-free systems

Exploration of the complex Ni-2(MBD)(4) (MBD = 2-mercaptobenzimidazole) (C1) having different coordinated Ni atoms as a photocatalyst for hydrogen evolution is made. For comparison, the bimetallic Ni-2(MBT)(4) (MBT = 2-mercaptobenthiazole) (C2) complex with the same coordinated Ni atoms was synthesized. Both of the complexes have been successfully constructed for photo-induced hydrogen production using organic dyes as photosensitizers and triethanolamine (TEOA) as the effective electron donor by visible light (>400 nm) in acetonitrile-water solution. The time-dependence of H-2 generation and DFT computational studies demonstrate that the complex C1 is more active than C2 for H-2 evolution. The mechanisms of photocatalytic hydrogen generation for C1 and C2 involve different protonation sites resulting from the differences between the two structures.