Two Novel Dinuclear Cobalt Polypyridyl Complexes in Electro- and Photocatalysis for Hydrogen Production: Cooperativity Increases Performance.

Syntheses and mechanisms of two dinuclear Co-polypyridyl catalysts for the H evolution reaction (HER) were reported and compared to their mononuclear analogue (R1). In both catalysts, two di-(2,2'-bipyridin-6-yl)-methanone units were linked by either 2,2'-bipyridin-6,6'-yl or pyrazin-2,5-yl. Complexation with Co gave dinuclear compounds bridged by pyrazine (C2) or bipyridine (C1).

Cobalt Complexes of Polypyridyl Ligands for the Photocatalytic Hydrogen Evolution Reaction.

The reductive part of artificial photosynthesis, the reduction of protons into H₂, is a two electron two proton process. It corresponds basically to the reactions occurring in natural photosystem I. We show in this review a selection of involved processes and components which are mandatory for making this light-driven reaction possible at all.

Light-Induced H Evolution with a Macrocyclic Cobalt Diketo-Pyrphyrin as a Proton-Reducing Catalyst.

Cobalt complexes are well-known catalysts for photocatalytic proton reduction in water. Macrocyclic tetrapyridyl ligands (pyrphyrins) and their Co complexes emerged in this context as a highly efficient class of H evolution catalysts. On the basis of this framework, a new macrocyclic Co complex consisting of two keto-bridged bipyridyl units (Co diketo-pyrphyrin) is presented.

Structure-Activity and Stability Relationships for Cobalt Polypyridyl-Based Hydrogen-Evolving Catalysts in Water.

A series of eight new and three known cobalt polypyridyl-based hydrogen-evolving catalysts (HECs) with distinct electronic and structural differences are benchmarked in photocatalytic runs in water. Methylene-bridged bis-bipyridyl is the preferred scaffold, both in terms of stability and rate. For a cobalt complex of the tetradentate methanol-bridged bispyridyl-bipyridyl complex [Co Br(tpy)]Br, a detailed mechanistic picture is obtained by combining electrochemistry, spectroscopy, and photocatalysis.