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Rhodium(I)-catalyzed cycloisomerization reactions of 1,6-allenynes with a tethered alkene (homoallylallene–alkyne substrate) or alkyne (homopropargylallene–alkyne substrate) have recently shown gre...

One-dimensional (1D) semiconductor nanorods are important for numerous applications ranging from optics and electronics to biology, yet the direct synthesis of high-quality metal halide perovskite nanorods remains a challenge. Here, we develop an intermediate monomer reservoir synthetic strategy to realize the controllable growth of uniform and low-defect CsPbBr3 perovskite nanorods. Intermediates composed of CsPb2Br5 and Cs3In2Br9 are obtained through the substitution of Pb2+ with In3+ cations in the template of CsPbBr3 nanocubes and act as a precursor reservoir to gradually release monomers, ensuring both the slow growth rate and low defects of nanorods. We have used branched tris(diethylamino)phosphine as a ligand, which not only has unequal binding energies with different crystal faces to promote the orientation growth but also provides strong steric hindrance to shield the nanorods in solution. Because of minor amount of defects and an effective ligand passivation, in addition to significantly enhanced stability, the perovskite nanorods show a high photoluminescence quantum yield of up to 90% and exhibit a net mode gain of 980 cm-1, the latter being a record value among all the perovskite materials. An extremely low amplified spontaneous emission threshold of 7.5 μJ cm-2 is obtained under excitation by a nanosecond laser, which is comparable to that obtained using femtosecond lasers in other recent studies.

There is a long-standing mechanistic consensus that alcohol oxidation by cytochrome P450 enzymes is triggered by hydrogen abstraction from the α-C–H bond of the alcohol. Through combined molecular ...

Synergetic optical resolution and chiral amplification of tetrahedral Ti4L6 cages by enantiopure coordination cations have been realized in this work. Anionic ΔΔΔΔ-[Ti4L6] and ΛΛΛΛ-[Ti4L6] cages (L...

BIF-20, a zeolite-like porous boron imidazolate framework with high density of exposed B–H bonding, is combined with graphitic carbon nitride (g-C3N4) nanosheets via a facile electrostatic self-assembly approach under room temperature, forming an elegant composite BIF-20@g-C3N4 nanosheet. The as-constructed composite preferably captures CO2 and further photoreduces CO2 in high efficiency. The photogenerated excitations from the carbon nitride nanosheet can directionally migrate to B–H bonding, which effectively suppresses electron–hole pair recombination and thus greatly improves the photocatalytic ability. Compared to the g-C3N4 nanosheet, the BIF-20@g-C3N4 nanosheet composite displayed a much-enhanced photocatalytic CO2 reduction activity, which is equal to 9.7-fold enhancements in the CH4 evolution rate (15.524 μmol g–1 h–1) and 9.85-fold improvements in CO generation rate (53.869 μmol g–1 h–1). Density functional theory simulations further prove that the presence of B–H bonding in the composite is fav...

Two new polar polyselenides Rb4Ge4Se12 (1) and Cs4Ge4Se12 (2) with rarely reported dimeric [Ge2Se4(μ-Se2)]4− units were synthesized. They present large second-harmonic generation (SHG) intensities of 7.5 and 6.5 times that of the benchmark AgGaS2 with type I phase-matching behavior, high laser induced damaged thresholds, wide transmission region and congruently melting behavior, making them excellent candidates for IR nonlinear optical (NLO) applications. The SHG functional motifs of both compounds are determined to be [Ge2Se4(μ-Se2)]4− unit by time-dependent density functional theory calculation, which further reveals that charge transfers from the lone pairs of terminal Se atoms to the five σ* orbitals of five-membered ring Ge2Se3 have a predominant contribution to the total SHG effect.

A rhodium-catalyzed azide–alkyne cycloaddition of internal ynamides is described. The reaction could be performed in a wide range of solvents, including aqueous media, under mild conditions without careful exclusion of air and moisture, giving a variety of 5-amino-triazoles as a single regioisomer. The mechanism of regioselective cycloaddition was rationalized by means of density functional theory calculations.

The solid oxide CO2 electrolyzer has the potential to provide storage solutions for intermittent renewable energy sources as well as to reduce greenhouse gas emissions. One of the key challenges remains the poor adsorption and activity toward CO2 reduction on the electrolyzer cathode at typical operating conditions. Here, we show a novel approach in tailoring a perovskite titanate (La, Sr)TiO3+δ cathode surface, by the in situ growing of SrO nanoislands from the host material through the control of perovskite nonstoichiometry. These nanoislands provide very enhanced CO2 adsorption and activation, with stability up to 800 °C, which is shown to be in an intermediate form between carbonate ions and molecular CO2. The activation of adsorbed CO2 molecules results from the interaction of exsolved SrO nanoislands and the defected titanate surface as revealed by DFT calculations. These cathode surface modifications result in an exceptionally high direct CO2 electrolysis performance with current efficiencies near 100%.

A manganese complex with a porphyrin-like ligand that catalyzes the highly chemoselective and enantioselective oxidation of heteroaromatic sulfides, including imidazole, benzimidazole, indole, pyridine, pyrimidine, pyrazine, sym-triazine, thiophene, thiazole, benzothiazole, and benzoxazole, with hydrogen peroxide is described, furnishing the corresponding sulfoxides in good to excellent yields and enantioselectivities (up to 90% yield and up to >99% ee) within a short reaction time (0.5 h). The practical utility of the method has been demonstrated in the gram-scale synthesis of chiral sulfoxide. Mechanistic studies, performed with 18O-labeled water (H218O), hydrogen peroxide (H218O2), and cumyl hydroperoxide, reveal that a high-valent manganese–oxo species is generated as the oxygen atom delivering agent via carboxylic acid assisted heterolysis of O–O bonds. Density functional theory (DFT) calculations were also carried out to give further insight into the mechanism of manganese-catalyzed sulfoxidation. O...

The enzyme SyrB2 employs an FeIV–oxo species to achieve selective C–H halogenation of l-threonine. Herein, we use combined quantum mechanical/molecular mechanical (QM/MM) calculations and molecular dynamics (MD) simulations to decipher the mechanism of selective halogenation by SyrB2. Our QM/MM calculations show the presence of three Cl–FeIV–oxo isomers which interconvert, and only the one having its oxo ligand pointing toward the target C–H bond is active during the hydrogen atom abstraction (H-abstraction) process. The fate of the formed Cl–FeIII–OH/R• intermediate is determined by a hydrogen-bonding interaction between the Arg254 residue and the OH ligand of Cl–FeIII–OH. The hydrogen bond not only prevents the OH group from participating in the followup rebound step to form a hydroxylated product but also facilitates the isomerization of the Cl–FeIII–OH/R• intermediate so that the Cl is directed toward the alkyl radical. The role of Arg254 in regulating the selectivity of chlorination is further discus...

DNA-base lesions cause cancer and propagate into the genome. We use in-protein QM/MM calculations to study the repair of etheno-bridged adenine (εA) by the iron(IV)-oxo species of AlkB enzymes. Recent experimental investigations, using mass-spectrometry and in crystallo isolation, suggested that εA was repaired by formation of an epoxide (εA-ep) that further transforms to a glycol (εA-gl), ending finally in adenine and glyoxal. Theory reproduces the experimentally observed barrier for the rate-determining step and its pH dependence. However, as we show, the mass-spectrometrically identified species are side-byproducts unassociated with the repair mechanism. The repair is mediated by a zwitterionic species, of the same molecular mass as the epoxide, which transforms to an intermediate that matches the in crystallo trapped species in structure and mass, but is NOT the assumed εA-gl iron-glycol complex. Verifiable/falsifiable predictions, regarding the key protein residues, follow. The paper underscores the indispensable role of theory by providing atomistic descriptions of this vital mechanism, and guiding further experimental investigations.

This work demonstrates that the Fe(III)(H2O2) complex, which has been considered as an unlikely oxidant in P450, is actually very efficient in sulfoxidation reactions. Thus, Fe(III)(H2O2) undergoes a low-barrier nucleophilic attack by sulfur on the distal oxygen, resulting in heterolytic O-O cleavage coupled to proton transfer. We further show that Fe(III)(H2O2) is an efficient sulfoxidation catalyst in synthetic iron porphyrin and iron corrolazine compounds. In all cases, Fe(III)(H2O2) performs the oxidation much faster than it converts to Cpd I and will therefore bypass Cpd I in the presence of a thioether. Thus, this paper not only suggests a plausible resolution of a longstanding issue in P450 chemistry regarding the "second oxidant" but also highlights a new mechanistic pathway for sulfoxidation reactions in P450s and their multitude of synthetic analogues. These findings have far-reaching implications for transition metal compounds, where H2O2 is used as the terminal oxidant.

This paper presents DFT calculations of C-H hydroxylation of N,N-dimethylaniline by Compound I (Cpd I) of cytochrome P450. The reaction involves two processes nascent from the two spin states of Cpd I, the low-spin (LS) and high-spin (HS) states. The calculations demonstrate that the kinetic isotope effects (KIEs) of the two processes are very different, and only KIELS fits the experimental datum. As such, KIE can be a sensitive probe of spin state reactivity.