A cobalt(Ⅱ)porphyrin with a tethered imidazole for efficient oxygen reduction and evolution electrocatalysis

Electrocatalytic oxygen reduction and evolution reactions are involved in new energy conversion and storage technologies,such as various fuel cells and metal-air batteries and also water splitting devices[1,2].However,both reactions are very slow in kinetics,and thus catalysts are required[3,4].

Recent progress in production and usage of hydrogen peroxide

Hydrogen peroxide has attracted increasing interest as an environmentally benign and green oxidant that can also be used as a solar fuel in fuel cells.This review focuses on recent progress in production of hydrogen peroxide by solar-light-driven oxidation of water by dioxygen and its usage as a green oxidant and fuel.The photocatalytic production of hydrogen peroxide is made possible by combining the e^(-)and 4e-oxidation of water with the e^(-)reduction of dioxygen using solar energy.The catalytic control of the selectivity of the e^(-)vs.4e-oxidation of water is discussed together with the selectivity of the e^(-)vs.4e-reduction of dioxygen.The combination of the photocatalytic e^(-)oxidation of water and the e^(-)reduction of dioxygen provides the best efficiency because both processes afford hydrogen peroxide.The solar-light-driven hydrogen peroxide production by oxidation of water and by reduction of dioxygen is combined with the catalytic oxidation of substrates with hydrogen peroxides,in which dioxygen is used as the greenest oxidant.

Nonheme Iron-Catalyzed Enantioselective cis-Dihydroxylation of Aliphatic Acrylates as Mimics of Rieske Dioxygenases

Enantioselective cis-dihydroxylation of alkenes represents an ideal route to synthesize enantioenriched syn-2,3-dihydroxy esters that are important structural motifs in numerous biologically and pharmaceutically relevant molecules.Bioinspired nonheme iron-catalyzed enantioselective cis-dihydroxylation meets the requirement of the modern synthetic chemistry from the atomic economy,green chemistry,and sustainable development perspectives.However,nonheme iron-catalyzed enantioselective cis-dihydroxylation is much underdeveloped because of the formidable challenges of controlling chemo-and enantioselectivities and product selectivity caused by the competitive epoxidation,cis-dihydroxylation,and overoxidation reactions.Herein,we disclose the fabrication of a biologically inspired nonheme iron complex-catalyzed enantioselective cis-dihydroxylation of multisubstituted acrylates using hydrogen peroxide(H_(2)O_(2))as the terminal oxidant by controlling the non-ligating or weakly ligating counterions of iron(Ⅱ)complexes,demonstrating a dramatic counteranion effect on the enantioselective cisdihydroxylation of olefins by H_(2)O_(2) catalyzed by nonheme iron complexes.A range of structurally disparate alkenes were transformed to the corresponding syn-2,3-dihydroxy esters in practically useful yields with exquisite chemo-and enantioselectivities(up to 99% ee).Given the mild and benign nature of this biologically inspired oxidation system as well as the ubiquity and synthetic utility of enantioenriched syn-2,3-dihydroxy esters as pharmaceuticals candidates and natural products,we expect that this strategy could serve as a promising complement to the well-known Sharpless asymmetric dihydroxylation,which is the chemical reaction of an alkene with OsO_(4) to produce a vicinal diol.