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Electrochemical CO2 reduction to valuable chemicals represents a green and sustainable approach to close the anthropogenic carbon cycle, but has been impeded by low efficiency and high cost of electrocatalysts. Here, a cost‐effective hybrid catalyst consisting of hemin (chloroprotoporphyrin IX iron(III)), a product recovered from bovine blood, adsorbed onto commercial Vulcan carbon is reported. Upon heat treatment, this material shows significantly improved activity and selectivity for CO2 reduction in water while exhibiting good stability for more than 10 h. The heat treatment leads to consecutive removal of the axial chlorine atom and decomposition of the iron porphyrin ring, restructuring to form atomic Fe sites. The optimized hybrid catalyst obtained at 900 °C shows near‐unity selectivity for reduction of CO2 to CO at a small overpotential of 310 mV. The insight into transformation of adsorbed Fe complexes into single Fe atoms upon heat treatment provides guidance for development of single atom catalysts. [ABSTRACT FROM AUTHOR]

Pentaarylpyridines were conveniently prepared in one step by pentafold Suzuki-Miyaura reactions of pentachloropyridine. Moreover, site selective reactions were performed, leading to various substituted arylpyridines. Pentaarylpyridines were studied in detail by means of DFT calculations and by optical spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: The direct electrochemistry of a HRP–chi–[C4mim][BF4] film (where HRP = horseradish peroxidase, chi = chitosan, and [C4mim][BF4] = the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluoroborate) has been studied by cyclic voltammetry on a glassy carbon electrode. The mechanism for the electrochemical reaction of HRP is suggested to be EC for the reduction, and CE for the following re-oxidation, as the oxidative peak potential remained approximately unchanged across the scan rate range. The half wave potential of HRP reduction was found to be pH dependent, suggesting that a concomitant proton and electron transfer is occurring. Using theoretical simulations of the experimentally obtained peak positions, the standard electron transfer rate constant, k 0, was found to be 98 (±16) s−1 at 295 K in pH 7 phosphate buffer solution, which is very close to the value reported in the absence of ionic liquid. This suggests that the ionic liquid used here in the HRP–chi–[C4mim][BF4]/GC electrode does not enhance the rate of electron transfer. k 0 was found to increase systematically with increasing temperature and followed a linear Arrhenius relation, giving an activation energy of 14.20 kJ mol−1. The electrode kinetics and activation energies obtained are identical to those reported for HRP films in aqueous media. This leads us to question if the use of RTIL films provide any unique benefits for enzyme/protein voltammetry. Rather the films may likely contain aqueous zones in which the enzymes are located and undergo electron transfer. [Copyright &y& Elsevier]

Herein we report the photo- and electrochemical characterization of pyrimidopteridine N-oxide-based heterocycles. The potential of their application as organic photoredox catalysts is showcased in the photomediated contra-thermodynamic E→Z isomerization of cinnamic acid derivatives and oxidative cyclization of 2-phenyl benzoic acid to benzocoumarin using molecular oxygen as a mild oxidant. Furthermore, unprecedented intermolecular non-covalent n-π-hole interactions in solid state are discussed based on crystallographic and theoretical data., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Selective aerobic oxidation of benzyl alcohol to benzaldehyde by a (bpy)Cu I (IM)/TEMPO catalyst (IM represents differently substituted imidazoles) has been studied by simultaneous operando electron paramagnetic resonance/UV-vis/attentuated total reflectance infrared spectroscopy in combination with cyclic voltammetry to explore the particular role of imidazole in terms of ligand and/or base as well as of its substitution pattern on the catalytic performance. For molar ratios of IM/Cu ≥ 2, a (bpy)Cu I/II (IM) a (IM) b complex is formed, in which the Cu-N distances and/or angles for the two IM ligands a and b are different. The coordination of a second IM molecule boosts the oxidation of Cu I to Cu II and, thus, helps to activate O 2 by electron transfer from Cu I to O 2 . The rates of Cu I oxidation and Cu II reduction and, thus, the rates of benzaldehyde formation depend on R of the R-N moiety in the IM ligand. Oxidation is fastest for R = H and alkyl, while reduction is slowest for R = H. The Cu I /Cu II interplay leads to decreasing total benzaldehyde formation rates in the order R (I+ effect) > R (conjugated system) > R = H.