Effects of metal centers of complexes supported by S,S′‐bis(2‐pyridylmethyl)‐1,2‐thioethane on catalytic activities for electrochemical‐ and photochemical‐driven hydrogen production

S,S′‐bis(2‐pyridylmethyl)‐1,2‐thioethane (bpte) reacts with MCl 2 (M = Co, Ni, and Fe) to give three complexes, namely, [Co II (bpte)Cl 2 ] ( 1 ), [Ni II (bpte)Cl 2 ] ( 2 ), and [Fe II (bpte)Cl 2 ] ( 3 ), respectively. They all act as catalysts for proton or water reduction to dihydrogen via electrolysis or photolysis. Under an overpotential of 837.6 mV, the electrolysis of a neutral buffer with complex 1 , 2 , or 3 can provide 418 (±3), 555 (±3), and 243 (±3) moles of hydrogen per mole of catalyst per hour (mol H 2 /mol catalyst/h), respectively. Under blue light, together with a photosensitizer and ascorbic acid (H 2 A) as a sacrificial electron donor, the photolysis of an aqueous solution (pH 4.5) containing complex 1 , 2 , or 3 can afford 9060 (±5), 24,900 (±5), and 10,630 (±5) moles H 2 per mole of catalyst (mol of H 2 [mol of cat] −1 ) during 83‐h irradiation with an average apparent quantum yield of 7.1%, 24%, and 10%, respectively. The results show that the nickel complex [Ni II (bpte)Cl 2 ] exhibits a more efficient activity for hydrogen generation than the iron or cobalt species. These findings may offer a new chemical paradigm for the design of efficient catalysts.