Construction and Enhanced Efficiency of Bi2MoO6/ZnO Compo-Sites for Visible-Light-Driven Photocatalytic Performance.

Bi2MoO6 was one of the important bismuth-based semiconductors with a narrow bandgap, and has been widely used in selective oxidation catalysts, supercapacitors, and energy-storage devices. A series of Bi2MoO6/ZnO composite photocatalysts with different mass ratios were synthesized by the hydrothermal method. The synthesized samples were characterized by XRD, PL, UV-Vis, SEM, TEM, XPS, and BET analysis techniques. Under visible light conditions, Methylene blue (MB) was used as the target degradation product to evaluate its photocatalytic performance. The results showed that the degradation rate constant of Bi2MoO6/ZnO (0.4-BZO) was about twice that of the traditional photocatalysis of ZnO. The Bi2MoO6/ZnO composite catalyst maintained stable performance after four consecutive runs. The high photocatalytic activity of Bi2MoO6/ZnO was attributed to the efficient electron transport of the heterojunction, which accelerates the separation of electron-hole pairs and reduces the probability of carrier recombination near the Bi2MoO6/ZnO heterojunction. Bi2MoO6/ZnO nanocomposites have potential applications in the field of photodegradation.

Which is the real oxidant in competitive ligand self-hydroxylation and substrate oxidation-a biomimetic iron(II)-hydroperoxo species or an oxo-iron(IV)-hydroxy one?

Nonheme iron(II)-hydroperoxo species (FeII-(η2-OOH)) 1 and the concomitant oxo-iron(IV)-hydroxyl one 2 are proposed as the key intermediates of a large class of 2-oxoglutarate dependent dioxygenases (e.g., isopenicillin N synthase). Extensive biomimetic experiments have been exerted to identify which one is the real oxidant and to reveal the structure-function relationship of them, whereas the mechanistic picture is still elusive. To this end, density functional theory (DFT) calculations were performed to systematically study the mechanistic details of ligand self-hydroxylation and competitive substrate oxidation by these two species supported by a tridentate ligand Fe(TpPh2)(benzilate) (TpPh2 = hydrotris(3,5-diphenylpyrazole-1-yl)borate). The calculated results revealed that the structure and the conversion of the FeII-(η2-OOH) complex 1 are obviously different from the ferric FeIII-OOH one. The orientation of the Fe-OOH moiety of 1 is side-on, while that of the ferric FeIII-OOH species is end-on. The conversion of 1 to the high-valent iron-oxo species is exothermic, while the conversion of the ferric FeIII-OOH species to the high-valent species is endothermic. Thus, the sluggish 1 does not act as the oxidant and readily decays to the robust 2. The activation energy of intramolecular ligand self-hydroxylation in 2 is 14.8 kcal mol-1 and intermolecular substrate oxidations (e.g., thioanisole sulfoxidation) with a lower barrier show a strong inhibiting ability toward ligand self-hydroxylation, while those with a higher barrier (e.g., cyclohexane hydroxylation) have no effect. Our theoretical results fit nicely with the experimental observations and will enrich the knowledge of the metal-oxygen intermediate and play a positive role in the rational design of new biomimetic catalysts.

Construction of Bi2S3-BiOBr nanosheets on TiO2 NTA as the effective photocatalysts: Pollutant removal, photoelectric conversion and hydrogen generation.

Novel energy material is the investigation focus to overcome the environment pollution and resource shortage crisis. TiO2 nanotube arrays (TiO2 NTA) could be used for pollutant decomposition, photoelectric conversion and H2, CH4 generation. BiOBr nanosheets were fabricated on TiO2 NTA by a solvothermal deposition method, and then transformed into Bi2S3 nanosheets after the ion exchange reaction. The results revealed that the ion concentration significantly influenced the morphology, microstructure, optical harvesting and photoelectrochemical capacity of Bi2S3-BiOBr/TiO2 NTA. The samples also exhibited high photocatalytic activity for the removal of dyes and Cr(VI), and the excellent photocurrent and photovoltage were obtained under visible light irradiation. The photocatalytic water splitting for hydrogen generation was carried out, and the photocatalytic hydrogen production rate achieved 17.26 µmol·cm-2·h-1. The photocatalyst showed the remarkable stability, and the photocatalytic ability still maintained high level after several repeated photocatalytic cycles. The photocatalytic data indicated that the Bi2S3-BiOBr/TiO2 NTA photocatalyst provided a perfect strategy for the sensitizer deposition on TiO2 NTA and novel approach for the photocatalytic performance improvement.

Synthesis, structure and photocatalytic property of a novel Zn(II) coordination polymer based on in situ synthetized pyridine-3,4-dicarboxylhydrazidate ligand.

One new pyridine-3,4-dicarboxylhydrazidate-coordinated compound [Zn(pdh)] 1 (pdh = pyridine-3,4-dicarboxylhydrazidate) was obtained under the hydrothermal conditions. Noteworthily, the pdh molecules in the title compound originated from the ligand in situ reaction between organic pyridine-3,4-dicarboxylic acid (pdca) and N2H4·H2O. X-ray single-crystal diffraction analysis revealed that the pdh ligands exhibit a special µ4-bridging mode in compound 1, which link Zn(II) centers into a 2D layered structure. The photocatalysis analysis indicates that it is a potential visible light catalyst. In addition, the solid photoluminescence property of compound 1 was also investigated.

4-Nitro-phenyl-hydrazinium picrate monohydrate.

In the crystal structure of the title compound, C6H8N3O2 (+)·C6H2N3O7 (-)·H2O, N-H⋯O and O-H⋯O hydrogen bonds link the components into a two-dimensional network parallel to (010). In addition, there are pairs of weak inversion-related C-H⋯O hydrogen bonds within the two-dimensional network. The three nitro groups are twisted by 1.6 (3), 7.8 (3) and 12.1 (3)° from the ring plane in the anion, while in the cation, the nitro group makes a dihedral angle of 4.6 (2)° with the ring.

What differs on the enzymatic acetylation mechanisms for arylamines and arylhydrazines substrates? A theoretical study.

The acetylation mechanisms of several selected typical substrates from experiments, including arylamines and arylhydrazines, are investigated with the density functional theory in this paper. The results indicate that all the transition states are characterized by a four-membered ring structure, and hydralazine (HDZ) is the most potent substrate. The bioactivity for all the compounds is increased in a sequence of PABA ≈ 4-AS < 4-MA < 5-AS ≈ INH < HDZ. The conjunction effect and the delocalization of the lone pairs of N atom play a key role in the reaction. All the results are consistent with the experimental data.

A density functional theory study on the role of His-107 in arylamine N-acetyltransferase 2 acetylation.

Arylamine N-acetyltransferases (NATs, EC 2.3.1.5) catalyze an acetyl group transfer from acetyl coenzyme A (AcCoA) to primary arylamines, and are responsible for the biotransformation and metabolism of drugs, carcinogens, etc. Structure analysis revealed that His-107 was likely the residue accountable for mediating acetyl transfer. We have examined the full catalytic mechanism of this system by means of DFT method. The results indicate that if the acetyl group directly transferred from the donor, p-nitrophenyl acetate, to the acceptor, cysteine, the high activation energy will be a great hindrance. These energies have dropped a little in a range of 20-25 kJ/mol when His-107 is assisting the transfer process. However, when protonated His-107 is mediating the reaction, the activation energies have dropped about 70-85 kJ/mol. Our calculations strongly support an enzymatic acetylation mechanism that experiences a thiolate-imidazolium pair, which have verified the presumption from experiments.

A quantum chemical study on the mechanism of glycinamide ribonucleotide transformylase inhibitor: 10-Formyl-5,8,10-trideazafolic acid.

A density functional theory (DFT) study is presented on the reaction mechanism of glycinamide ribonucleotide (GAR) with 10-formyl-5,8,10-trideazafolic acid (10f-TDAF), which is an inhibitor designed for GAR transformylase (GAR Tfase). There are three different paths for this system and the results indicate that inhibitor 10f-TDAF can form a very stable intermediate with the substrate GAR or generate an imine bond with GAR by elimination of water. The results have verified the presumption from available experiments and implied that 10f-TDAF would be an important target for anti-neoplastic intervention.

A quantum chemical study of the water-assisted mechanism in one-carbon unit transfer reaction catalyzed by glycinamide ribonucleotide transformylase.

A theoretical study for the water-assisted mechanism in one-carbon unit transfer reaction catalyzed by glycinamide ribonucleotide transformylase (GAR Tfase) is investigated in which the proton transfers in an indirect way and the energy barrier for each transition state has been lowered about 80-100 kJ/mol when compared with the corresponding one in a no-water-involved mechanism. There are two possible pathways in each mechanism: one is concerted and the other is stepwise. Our results have verified the presumption from experiments that one water molecule can assist to achieve the whole reaction. Because the addition of this water molecule in the transition states can relax the strong strain in the unstable system and greatly lowered the energy barrier. The water-assisted paths are preferable to the no-water-involved ones and the bulk solvent effect of water is also discussed.