Cover Feature: Ligand Substituent Effects on Light‐Driven Hydrogen Evolution by Cobalt(II) Tripodal Iminopyridine Catalysts under Precious‐Metal‐Free Conditions (Eur. J. Inorg. Chem. 31/2022)

The Cover Feature shows light-driven hydrogen evolution mediated by cobalt(II) tripodal iminopyridine complexes, using tri(n-butyl)triazatriagulenium (TATA+) as the organic sensitizer and triethylamine (TEA) as the sacrificial donor in aqueous acetonitrile. The activity of the complexes depends highly on the electronic properties of the substituents on the pyridine moieties. Under acidified conditions, the activity for H2 production was enhanced for the substituted catalysts. The 5-Cl derivative showed higher activity and lower catalytic potential (Ecat), which can be attributed to the stabilized CoI, favorable for the formation of CoIII(H). The improved H2 productivity and lower Ecat of the 5-CH3O, 6-CH3O, and 5-CH3 derivatives are suggested to be associated with the increased electron density on the CoIII(H) intermediate, which is more susceptible to protonation. More information can be found in the Research Article by J. Xiang, C.-F. Leung, C.-C. Ko and co-workers.