Search

Developing chiral electrode catalysts for enantioselective electrosynthesis is a great challenge, as it requires catalysts that possess both high activity and enantioselectivity. Precise synthesis of nanoclusters and single atoms coexisting chiral catalysts provide a promising pathway for enhancing asymmetric catalytic performance. Herein, chiral electrode catalysts are fabricated comprising gold clusters (R‐AuC) and single atoms (R‐AuS) on graphene oxide (R‐AuC/S@GO) through an assembly‐irradiation strategy. Thereinto, the R‐Aus is in situ generated from R‐AuC under light irradiation. The monoatomization process can be precisely regulated by changing the wavelength of the light, resulting in four Au‐based chiral electrode (R‐Au@GO) catalysts with different ratios of nanoclusters and single atoms. These chiral electrodes are applied in the electrocatalytic enantioselective hydrogenation of methyl benzoylformate (MB) to chiral methyl mandelate (S‐MM), and the R‐AuC/S‐2@GO with ≈26% R‐AuC and 74% R‐AuS achieve the highest catalytic activity (35 µmol cm−2 h−1 productivity) and enantioselectivity [97% enantiomeric excess (ee)]. Detailed experimental analysis and density functional theory calculations reveal that the R‐AuS on GO promotes the in situ generation of H* species, and R‐AuC mainly drives the enantioselective conversion of MB by transferring the H* species to the carbonyl group of MB, ultimately yielding chiral S‐MM. [ABSTRACT FROM AUTHOR]

Density functional theory calculation is used to investigate the oxidation of cyclo-olefin (cyclobutene, cyclopentene, cyclohexene, cycloheptene, and cyclo-octene) by the complex [FeIV(O)(TQA)(NCMe)]2+, which has S = 2 ground state, and the effect of electronic factors and steric hindrance on reaction barriers. Our results suggest that the oxo–iron(IV) complex can oxidise C–H and C = C bonds via a single-state mechanism, and two different ways of electron transport exist. The energy barriers initially decrease with increasing substrate size, and the trend then reverses. Comparison of the energy barrier in different systems reveals that except for the reaction between [FeIV(O)(TQA)(NCMe)]2+ and cycloheptene, oxo–iron(IV) complexes prefer epoxidation to hydroxylation. However, the hydroxylated product is more stable than the corresponding epoxidated product. This result indicates that the products of epoxidation tend to decompose first. The energy barrier of hydroxylation and epoxidation originates from the balance of orbital interaction and Pauli repulsion from the equatorial ligand and protons on the approaching substrate. In this regard, we calculate the weak interaction between two fragments (oxo–iron complex and substrates) using the independent gradient model and drawn the corresponding 3D isosurface representations of reactants. [ABSTRACT FROM AUTHOR]

• Using DFT and TD-DFT to unveil the ESIPT mechanism of HAN. • Revealing the effect of intermolecular hydrogen-bonds on ESIPT and fluorescence. • The reason why HAN has weak fluorescence in aqueous solution was unveiled. • The hydrogen bond dynamics in the different microenvironment upon excitation was showed. 1′-hydroxy-2′-acetonaphthone (HAN) is a useful fluorescence probe based on excited state intramolecular proton transfer (ESIPT). A number of experiments had explored the fluorescence properties of HAN in different microenvironments and applied HAN to bioimaging. However, the mechanism of fluorescence properties of HAN in different microenvironments was not been fully reported. Thus, our research aims to investigate the proton transfer (PT) and fluorescence characteristics of HAN in different microenvironments, focusing on revealing the hydrogen bond dynamics in high-polar aqueous solution (HAN-H 2 O) and low-polar hydrophobic pocket of bovine serum albumin by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Explicit water molecules were placed around HAN to simulate the hydrogen bond interactions between HAN and the water molecules in an aqueous solution. The intermolecular hydrogen bonds slightly affect the geometric structures of HAN, but would inhibit the ESIPT process while increasing the charge transfer distance, leading to red shift of fluorescence. Upon photoexcitation, the intramolecular hydrogen bond had been strengthened, providing the driving force of PT, which resulted in HAN and HAN-H 2 O undergoing ultrafast ESIPT process. Meanwhile, after photoexcitation, the intermolecular hydrogen bonds were significantly enhanced, decreasing the energy of HAN-H 2 O in the excited state and promoted the radiationless deactivation of HAN-H 2 O. Therefore, HAN has weak fluorescence in the aqueous solution. [ABSTRACT FROM AUTHOR]

• Expect syn -AN, the ligand topology exhibits little effect on the reactivity. • Along the reaction pathway, the AN ligand is away from the iron center. • The relative reactivity of the O-transfer reaction follows the order: syn -AN > syn -TF > syn -N3 > syn -SR. This paper has used density functional theory to investigate the oxygen-transfer reactivity of a series of non-heme [FeIV(O anti/syn)(TMC)(L ax)]n+ (anti/syn -L ax) complexes, toward the trimethylphosphine, and has described their geometric and electronic structures. The reactions have been dominated by the S = 2 state. There are no significant steric hindrance of the FeIV O⋯H distances and H-O-Fe angles for the anti/syn -L ax complexes. Especially, syn -AN, which has the neuter axial ligand, is the most reactive in all complexes, and the process of the syn -AN occurs spontaneously. The relative reactivity of the O-transfer reaction follows the order: syn -AN > syn -TF > syn -N3 > syn -SR. [ABSTRACT FROM AUTHOR]