Molecular quaterpyridine-based metal complexes for small molecule activation: water splitting and CO reduction.

Artificial photosynthesis is considered as one of the most promising strategies for solar-to-fuel conversion through sunlight-driven water splitting and CO2 reduction. This tutorial describes recent developments in the use of metal quaterpyridine complexes as electrocatalyts and photocatalysts for artificial photosynthesis.

An Iron Quaterpyridine Complex as Precursor for the Electrocatalytic Reduction of CO to Methane.

A Fe quaterpyridine complex was used as a molecular precursor for the electrochemical reduction of CO to CH in acetonitrile in the presence of triethanolamine. CH was produced with a faradaic yield of approximately 2.1 % at 25 °C and 1 atm pressure of CO as reactant.

A Carbon Nitride/Fe Quaterpyridine Catalytic System for Photostimulated CO-to-CO Conversion with Visible Light.

Efficient and selective photostimulated CO-to-CO reduction by a photocatalytic system consisting of an iron-complex catalyst and a mesoporous graphitic carbon nitride (mpg-CN) redox photosensitizer is reported for the first time. Irradiation in the visible region (λ ≥ 400 nm) of an CHCN/triethanolamine (4:1, v/v) solution containing [Fe(qpy)(HO)] (qpy = 2,2':6',2'':6'',2''-quaterpyridine) and mpg-CN resulted in CO evolution with 97% selectivity, a turnover number of 155, and an apparent quantum yield of ca. 4.

Photocatalytic Conversion of CO to CO by a Copper(II) Quaterpyridine Complex.

The invention of efficient systems for the photocatalytic reduction of CO comprising earth-abundant metal catalysts is a promising approach for the production of solar fuels. One bottleneck is to design highly selective and robust molecular complexes that are able to transform the CO gas. The Cu quaterpyridine complex [Cu(qpy)] (1) is found to be a highly efficient and selective catalyst for visible-light driven CO reduction in CH CN using [Ru(bpy) ] (bpy: bipyridine) as photosensitizer and BIH/TEOA (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole/triethanolamine) as sacrificial reductant.

Local Proton Source in Electrocatalytic CO Reduction with [Mn(bpy-R)(CO) Br] Complexes.

The electrochemical behavior of fac-[Mn(pdbpy)(CO) Br] (pdbpy=4-phenyl-6-(phenyl-2,6-diol)-2,2'-bipyridine) (1) in acetonitrile under Ar, and its catalytic performances for CO reduction with added water, 2,2,2-trifluoroethanol (TFE), and phenol are discussed in detail. Preparative-scale electrolysis experiments, carried out at -1.5 V versus the standard calomel electrode (SCE) in CO -saturated acetonitrile, reveal that the process selectivity is extremely sensitive to the acid strength, producing CO and formate in different faradaic yields.