Interface engineering has been recognized as one of the most promising strategies for regulating the physical and chemical properties of materials. However, constructing well‐defined nanointerfaces ...with efficient oxygen evolution reaction (OER) still remains a challenge. Herein, cross columnar NiTe nanoarrays supported on nickel foam are prepared. Subsequently, NiTe/NiS nanointerfaces are constructed by an ion‐exchange process. Importantly, the electrocatalytic performance for the OER can be facilitated by coupling NiTe and NiS. As a result, NiTe/NiS shows excellent OER activity with an ultralow overpotential of only 257 mV at a current density of 100 mA cm−2, and a Tafel slope of 49 mV dec−1 in 1.0 m KOH. The calculated and experimental results reveal that the strong electron interaction on nanointerfaces induces electronic structure modulation, which optimizes the binding energy of *OOH intermediates, thus improving the OER performance.
Cross columnar NiTe/NiS heterojunction nanoarrays are constructed by coupling NiTe and NiS nanodots. The strong electron interaction on nanointerfaces induces electronic structure modulation, thus improving the oxygen evolution reaction (OER) performance.
The first example of room temperature non-noble metal homogeneous system catalyzed selective N-alkylation of anilines with alcohols by a bis-NHC manganese complex is presented. This system was ...applied to a large range of alcohols and anilines, including biologically relevant motifs and challenging methanol. Experimental and computational studies suggest an outer-sphere mechanism for this NHC-Mn system.
Glycerol is one of the important biomass‐derived feedstocks and the high‐value utilizations of glycerol have attracted much attentions in recent years. Herein, we report a manganese catalyzed ...dehydrogenative coupling of glycerol with amines for the synthesis of substituted 2‐methylquinoxalines, 2‐ethylbenzimidazoles, and α‐aminoketones without any external oxidant. In these reactions, NHC‐based pincer manganese complex featuring a pyridine backbone displayed high catalytic activity and selectivity, in which hydrogen and water were produced as the only by‐products using glycerol as a C3 synthon.
A manganese‐catalyzed dehydrogenative coupling of glycerol with amines for the synthesis of substituted 2‐methylquinoxalines, 2‐ethylbenzimidazoles, and α‐aminoketones was reported. NHC‐based pincer manganese complex featuring a pyridine backbone displayed high catalytic activity and selectivity. No external oxidants were used in these reactions and hydrogen and water were produced as the only by‐products.
Disclosed herein is a novel, redox‐neutral protocol for the visible‐light‐induced radical alkynylation of unactivated olefins. The intramolecular migration of an alkynyl group, by cleaving an inert ...C−C σ bond, is realized for the first time. A wide range of synthetically useful trifluoroethylated linear alkynes are readily obtained under mild reaction conditions.
1+1>2: A redox‐neutral protocol for the visible‐light catalyzed radical alkynylation of unactivated olefins is disclosed. The intramolecular migration of an alkynyl group, by cleaving an inert C−C σ bond, is realized for the first time. A broad range of synthetically useful trifluoroethylated linear alkynes are efficiently produced under mild reaction conditions.
Gold allenylidene species have been seldom exploited as reactive intermediates in synthetically versatile catalytic reactions. By employing alkynylbenziodoxoles as the substrates and bifunctional ...WangPhos as the metal ligand, this work demonstrated ready catalytic access to these intermediates of general substitution patterns and their electrophilic reactivities at the γ‐carbon center with a diverse range of nucleophiles. The reaction is driven by the reductive decomposition of the benziodoxole moiety and achieves the replacement of a propargylic proton with an N/O/C‐based nucleophile, hence realizing reactivity umpolung. Corroborated by Density Functional Theory (DFT) calculations, the reaction mechanism involves a mild propargylic deprotonation. In contrast to prior works employing a tertiary amine functionality, a weakly BrØnsted‐basic amide group in WangPhos is surprisingly effective in deprotonation at the propargylic position under a gold‐ligand cooperation regime.
Reactive gold allenylidenes are catalytically generated via ligand‐enabled redox decomposition of alkynylbenziodoxole substrates. In cooperation with gold, a remote amide group in the biphenyl‐2‐ylphosphine ligand is remarkably capable of deprotonating at the propargylic position. DFT calculations offer support to the proposed mechanism.
The ONIOM Method and Its Applications Chung, Lung Wa; Sameera, W. M. C; Ramozzi, Romain ...
Chemical reviews,
06/2015, Letnik:
115, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Chung et al present an in-depth investigation of the ONIOM method and related method developments. They focus on applications of the ONIOM method to organic systems, inorganic compoounds and ...homogeneous catalysis, heterogeneous catalysis, nanomaterials, excited states, solution chemistry, and biological macromolecules.
The Guerbet reaction is important for the synthesis of longer‐chain monoalcohols like isobutanol through catalytic transfer hydrogenation from short‐chain methanol and ethanol. However, the mechanism ...becomes complicated, especially considering the variations in the different metal‐ligand cooperation (MLC) catalysts used. In order to further understand the Guerbet reaction, DFT studies were performed to figure out the detailed mechanism initiated by the unique Mn‐PCP MLC Catalyst. Our results suggest that even with the assistance of the carbanion site of the PCP ligand, the direct substitution mechanism is less favored than the condensation‐reduction mechanism. The key step of the reaction is the final reduction of the carbonyl, in which the 1,4‐reduction of the unsaturated aldehyde is prior to the 3,4‐reduction or 1,2‐reduction due to the stronger interaction between the catalyst and the substrate. It is found that the production of isobutanol is preferred over n‐butanol because of the lower total free energy barrier and lower relative free energy of the product. Finally, by changing the electronic effect of the carbanion site of the catalyst, we found that the relation between the electronic effect and the highest free energy span was not monotonous and a point with optimal electronic effect exists numerically.
DFT study provides insights into the mechanism of Guerbet reaction by metal‐ligand cooperation catalyst Mn‐PCP. The selectivity and the electronic effect of the carbanion PCP ligand on the Guerbet reaction were elucidated.
Metal ligand cooperation (MLC) catalysis is a popular strategy to design highly efficient transition metal catalysts. In this presented theoretical study, we describe the key governing factor in the ...MLC mechanism, with the Szymczak’s NNN-Ru and the Milstein’s PNN-Ru complexes as two representative catalysts. Both the outer-sphere and inner-sphere mechanisms were investigated and compared. Our calculated result indicates that the PNN-Ru pincer catalyst will be restored to aromatic state during the catalytic cycle, which can be considered as the driving force to promote the MLC process. On the contrary, for the NNN-Ru catalyst, the MLC mechanism leads to an unfavored tautomerization in the pincer ligand, which explains the failure of the MLC mechanism in this system. Therefore, the strength of the driving force provided by the pincer ligand actually represents a prerequisite factor for MLC. Spectator ligands such as CO, PPh3, and hydride are important to ensure the catalyst follow a certain mechanism as well. We also evaluate the driving force of various bifunctional ligands by computational methods. Some proposed pincer ligands may have the potential to be the new pincer catalysts candidates. The presented study is expected to offer new insights for MLC catalysis and provide useful guideline for future catalyst design.
Optically active organoboronic acids and their derivatives are an important family of target compounds in organic chemistry, catalysis, and medicinal chemistry. Yet there are rare asymmetric ...catalytic examples reported for the synthesis of these compounds via atom and step economic ways. Herein, we report a chelate-directed iridium-catalyzed asymmetric C(sp2)–H borylation of aromatic C–H bonds directed by free amine groups. The success of these transformations relies on a novel family of chiral bidentate boryl ligands (L). They can be synthesized straightforwardly in three steps starting from readily available (S,S)-1,2-diphenyl-1,2-ethanediamie ((S,S)-DPEN). The Ir-catalyzed C(sp2)–H borylation comprises two parts. The first part is desymmetrization of prochiral diarylmethylamines. In the presence of L3/Ir, a vast array of corresponding borylated products were obtained with high regioselectivity and good to excellent enantioselectivities (26 examples, up to 96% ee). The second part, kinetic resolution of racemic diarylmethylamines, was also conducted. Good selectivity values (up to 68%, 11 examples) were obtained when L8 was used. We also demonstrated the synthetic utility of the current method on gram-scale reaction for several transformations. The C–B bonds of borylated products could be converted to a variety of functionalities including C–O, C–C, C–C, C–Br, and C–P bonds. Finally, we performed DFT calculations of desymmetrization to understand its reaction pathways.
Photosynthesis of hydrogen peroxide (H
O
) in ambient conditions remains neither cost effective nor environmentally friendly enough because of the rapid charge recombination. Here, a photocatalytic ...rate of as high as 114 μmol⋅g
⋅h
for the production of H
O
in pure water and open air is achieved by using a Z-scheme heterojunction, which outperforms almost all reported photocatalysts under the same conditions. An extensive study at the atomic level demonstrates that Z-scheme electron transfer is realized by improving the photoresponse of the oxidation semiconductor under visible light, when the difference between the Fermi levels of the two constituent semiconductors is not sufficiently large. Moreover, it is verified that a type II electron transfer pathway can be converted to the desired Z-scheme pathway by tuning the excitation wavelengths. This study demonstrates a feasible strategy for developing efficient Z-scheme photocatalysts by regulating photoresponses.
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