The active site of [FeFe]-hydrogenase (H 2 ase) is preorganized with an amine (azadithiolate) as ap roton relay and a[4Fe4S] subunit as an electron reservoir,whichtogether lower the overpotential for proton reduction and hydrogen oxidation by multiple-site concerted proton-electron transfer (MS-CPET). Herein, we report am ononuclear manganese complex, fac-[Mn(CO) 3 (6-(2-hydroxyphenol)-2-pyridine-2quinoline) Br] (1), as arare model to fully mimic the functions of the H 2 ase.I n1,aredox-active bidentate ligand with ap endent phenol replicates the roles of the electron reservoir and the proton relayi nt he enzyme.E xperimental and theoretical studies revealed two consecutive MS-CPET processes in the catalytic cycle,ineach of whichanelectron stored in the reductive ligand and ap roton at the proximal phenol moiety are transferred to the Mn center in aconcerted way.By virtue of this mechanism, complex 1 exhibited al ow overpotential comparable to that of natural enzyme in electrochemical hydrogen production using phenol as ap roton source.

A series of manganese polypyridine complexes were prepared as CO2 reduction electrocatalysts. Among these catalysts, the intramolecular proton tunneling distance for metal hydride formation (PTD‐MH) vary from 2.400 to 2.696 Å while the structural, energetic, and electronic factors remain essentially similar to each other. The experimental and theoretical results revealed that the selectivity of CO2 reduction reaction (CO2RR) is dominated by the intramolecular PTD‐MH within a difference of ca. 0.3 Å. Specifically, the catalyst functionalized with a pendent phenol group featuring a slightly longer PTD‐MH favors the binding of proton to the [Mn−CO2] adduct rather than the Mn center and results in ca. 100 % selectivity for CO product. In contrast, decreasing the PTD‐MH by attaching a dangling tertiary amine in the same catalyst skeleton facilitates the proton binding on the Mn center and switches the product from CO to HCOOH with a selectivity of 86 %.

A manganese terpyridine complex 1 with a coordinated carboxylate in the axial position was obtained in situ. By virtue of a hangman effect, complex 1 catalyzes electrochemical hydrogen evolution from...

[FeFe]-hydrogenases (H2ase) catalyze hydrogen evolution reaction (HER) with excellent performances that rival that of platinum, the active site of which is built with crucial structural features required for efficient H−H...