Mechanistic Study for the Reaction of B12 Complexes with m-Chloroperbenzoic Acid in Catalytic Alkane Oxidations

Manganese(II) Porphyrin and Cumyl Hydroperoxide: An Efficient Catalyst for Aryl-Pentazole C-N Bond Cleavage

The selective cleavage of C-N bonds in N-containing compounds holds significant research value in organic synthesis, particularly for the synthesis of promising polynitrogen species. For instance, the discovery of the cyclo-pentazolate (cyclo-N5 -) anion in 2017 as a result of cleavage of the C-N bond has sparked interest within the field of high energy density materials. However, previous methods using ferrous glycinate and m-chloroperoxybenzoic acid generated the cyclo-N5 - anion in a low yield of 19.5 % after 24 hours, and the mechanism remained unclear. In this study, we developed an efficient catalytic system comprising Mn (II) tetraphenylporphyrin and cumyl hydroperoxide. This system enables the cyclo-N5 - anion to be produced from 3,5-dimethyl-4-hydroxyphenylpentazole in 35.4 % yield in 4 hours. Characterization of Mn(IV)-oxo porphyrins, ⋅CH3, and ⋅C8H8ON5 radicals provides evidence for the mechanism whereby the cyclo-N5 - anion forms. Our study underscores the competitive potential of radical-initiated selective C-N bonds cleavage in N-arylazoles and opens avenues for further exploration in this field.

A synthetically useful catalytic system for aliphatic C-H oxidation with a nonheme cobalt complex and m-CPBA

We report herein a synthetically useful catalytic system for aliphatic C-H oxidation with a mononuclear nonheme cobalt(II) complex and m-chloroperbenzoic acid (m-CPBA). Preliminary mechanistic studies suggest that a high-valent cobalt-oxygen species (e.g., cobalt(IV)-oxo or cobalt(III)-oxyl) is the oxidant that effects C-H oxidation via a rate-determining hydrogen atom abstraction (HAA) step.

Gas diffusion enhanced electrode with ultrathin superhydrophobic macropore structure for acidic CO2 electroreduction

Carbon dioxide (CO2) electroreduction reaction (CO2RR) offers a promising strategy for the conversion of CO2 into valuable chemicals and fuels. CO2RR in acidic electrolytes would have various advantages due to the suppression of carbonate formation. However, its reaction rate is severely limited by the slow CO2 diffusion due to the absence of hydroxide that facilitates the CO2 diffusion in an acidic environment. Here, we design an optimal architecture of a gas diffusion electrode (GDE) employing a copper-based ultrathin superhydrophobic macroporous layer, in which the CO2 diffusion is highly enhanced. This GDE retains its applicability even under mechanical deformation conditions. The CO2RR in acidic electrolytes exhibits a Faradaic efficiency of 87% with a partial current density [Formula: see text] of -1.6 A cm-2 for multicarbon products (C2+), and [Formula: see text] of -0.34 A cm-2 when applying dilute 25% CO2. In a highly acidic environment, C2+ formation occurs via a second order reaction which is controlled by both the catalyst and its hydroxide.

Effect of Macrocycles on the Photochemical and Electrochemical Properties of Cobalt-Dehydrocorrin Complex: Formation and Investigation of Co(I) Species

Co(II)-pyrocobester (P-Co(II)), a dehydrocorrin complex, was semisynthesized from vitamin B12 (cyanocobalamin), and its photochemical and electrochemical properties were investigated and compared to those of the cobester (C-Co(II)), the cobalt-corrin complex. The UV-vis absorptions of P-Co(II) in CH2Cl2, ascribed to the π-π* transition, were red-shifted compared to those of C-Co(II) due to the π-expansion of the macrocycle in the pyrocobester. The reversible redox couple of P-Co(II) was observed at E1/2 = -0.30 V vs Ag/AgCl in CH3CN, which was assigned to the Co(II)/Co(I) redox couple by UV-vis, ESR, and molecular orbital analysis. This redox couple was positively shifted by 0.28 V compared to that of C-Co(II). This is caused by the high electronegativity of the dehydrocorrin macrocycle, which was estimated by DFT calculations for the free-base ligands. The reactivity of the Co(I)-pyrocobester (P-Co(I)) was evaluated by the reaction with methyl iodide in CV and UV-vis to form a photosensitive Co(III)-CH3 complex (P-Co(III)-CH3). The properties of the excited state of P-Co(I), *Co(I), were also investigated by femtosecond transient absorption (TA) spectroscopy. The lifetime of *Co(I) was estimated to be 29 ps from the kinetic trace at 587 nm. The lifetime of *Co(I) became shorter in the presence of Ar-X, such as iodobenzonitrile (1a), bromobenzonitrile (1b), and chlorobenzonitrile (1c), and the rate constants of electron transfer (ET) between the *Co(I) and Ar-X were determined to be 2.9 × 1011 M-1 s-1, 4.9 × 1010 M-1 s-1, and 1.0 × 1010 M-1 s-1 for 1a, 1b, and 1c, respectively.