Transition-metal-catalyzed C–N
bond-forming reactions have
emerged as fundamental and powerful tools to construct arylamines,
a common structure found in drug agents, natural products, and fine
chemicals. Reported herein is an alternative access to heteroarylamine
via radical–radical cross-coupling pathway, powered by visible
light catalysis without any aid of external oxidant and reductant.
Only by visible light irradiation of a photocatalyst, such as a metal-free
photocatalyst, does the cascade single-electron transfer event for
amines and heteroaryl nitriles occur, demonstrated by steady-state
and transient spectroscopic studies, resulting in an amine radical
cation and aryl radical anion in situ for C–N bond formation.
The metal-free and redox economic nature, high efficiency, and site-selectivity
of C–N cross-coupling of a range of available amines, hydroxylamines,
and hydrazines with heteroaryl nitriles make this protocol promising
in both academic and industrial settings.
Inspired by the cubic Mn CaO cluster of natural oxygen-evolving complex in Photosystem II, tetrametallic molecular water oxidation catalysts, especially M O cubane-like clusters (M=transition metals), have aroused great interest in developing highly active and robust catalysts for water oxidation. Among these M O clusters, however, copper-based molecular catalysts are poorly understood. Now, bio-inspired Cu O cubanes are presented as effective molecular catalysts for electrocatalytic water oxidation in aqueous solution (pH 12). The exceptional catalytic activity is manifested with a turnover frequency (TOF) of 267 s for [(L -Cu) ] at 1.70 V and 105 s for [(L -Cu) ] at 1.56 V. Electrochemical and spectroscopic study revealed a successive two-electron transfer process in the Cu O cubanes to form high-valent Cu and Cu O intermediates during the catalysis.
Semiconductor quantum dots (QDs) in conjunction with non-noble 3d-metal ions (e.g., Fe 3+ , Co 2+ , and Ni 2+ ) have emerged as an extremely efficient, facile, and cost-effective means of solar-driven hydrogen (H 2 ) evolution. However, the exact structural change of the active sites under realistic conditions remains elusive, and the mechanism of H 2 evolution behind the remarkable activity is poorly understood. Here, we successfully track the structural variation of the catalytic sites in the typical H 2 photogeneration system consisting of CdSe/CdS QDs and 3d-metal ions (i.e., Ni 2+ used here). That is, the nickel precursor of Ni(OAc) 2 changes to Ni(H 2 O) 6 2+ in neutral H 2 O and eventually transforms to Ni(OH) 2 nanosheets in alkaline media. Furthermore, the in operando spectroscopic techniques of electron paramagnetic resonance and X-ray absorption spectroscopy reveal the photoinduced transformation of Ni(OH) 2 to a defective structure [Ni x 0 /Ni 1−x (OH) 2 ], which acts as the real catalytic species of H 2 photogeneration. Density functional theory (DFT) calculations further indicate that the surface Ni-vacancies (V Ni ) on the Ni(OH) 2 nanosheets enhance the adsorption and dissociation of H 2 O molecules to enhance the local proton concentration, while the Ni 0 clusters behave as H 2 -evolution sites, thereby synergistically promoting the activity of H 2 photogeneration in alkaline media.
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