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. The design and the performances of the water reduction catalysts is a main focus together with the question about electron relays or sacrificial electron donors. It is shown how an original catalyst is developed into better ones and what it needs to move from purely academic homogeneous processes to heterogeneous systems. The importance of detailed mechanistic knowledge obtained from kinetic data is emphasized.

Improving the overall performance of photochemical H2 evolution catalyzed by the Co-NHC complex via the redox tuning of electron relays

The catalytic performance of photochemical H2 evolution from water by Co-NHC-1 is dramatically improved by rational redox tuning of an electron relay.

Refuting the ideas advocated by Yuly et al. (PNAS, Sep. 2020): ‘Universal free energy landscapes’ and ‘deterministic electron-relay circuitry’ are unsustainable within membrane-embedded cytochrome b protein complexes involved in bioenergetic routines

This communication discusses the interactions/outcomes of isoprenoid quinones/quinols (Q/QH2) and membrane-bound cytochromes involved in bioenergetic routines. Particularly, we use qualitative and quantitative arguments to counter the idea that highly deterministic electron relays are triggered within Complex III of mitochondria, resulting from the donation of two electrons by QH2 (Yuly et al., PNAS, 2020). In this regard, we propose that murburn concept explains the role(s) of membrane-embedded Q/QH2 in vital metabolic processes such as mitochondrial oxidative phosphorylation (OxPhos) and chloroplastid/cyanobacterial photophosphorylations (PhotoPhos), without invoking highly fastidious universal free energy landscapes or deterministic electron circuitry.