DFT study on the synthesis of trifluoroacetophenone from palladium complex LPd(Ph)CF (L = Xantphos or DtBPF) and CO.

The carbonylative trifluoromethylation reaction mechanism of palladium complex LPd(Ph)CF (L = Xantphos or DtBPF) and CO to synthesize trifluoroacetophenone was calculated using the density functional theory B3LYP method. In this paper, we conducted a computational study on the competition mechanism of two different products trifluorotoluene and trifluoroacetophenone. The calculation result reveals (1) CO insertion and reduction-elimination are two key steps in palladium-catalyzed reactions; (2) for the palladium complex (Xantphos)Pd(Ph)CF, the resulting product trifluoroacetyl has a lower activation energy and higher reactivity; and (3) for the metal palladium ligand DtBPF, the small energy difference between the two products indicates that the stereoselectivity of the product is relatively poor.

The efficacy and safety of intermittent preventive treatment with sulphadoxine-pyrimethamine vs artemisinin-based drugs for malaria: a systematic review and meta-analysis.

Background: Malaria is one of the most serious global problems. The objective of this study is to assess whether intermittent preventive treatment (IPT) using artemisinin-based combination therapies (ACTs) was a promising alternative to IPT with sulphadoxine-pyrimethamine (IPT-SP).

Methods: We searched the following sources up to 12 August 2020: PubMed, The Cochrane Library, Embase, Web of Science, CNKI, CBM, VIP and WanFang Database from inception.

Core-shell shaped NiCoHCF@PPy microspheres from prussian blue analogues for high performance asymmetric supercapacitors.

Recently, prussian blue analogues (PBAs), as the most classical class of metal-organic frameworks, have been widely studied by scientists. Nevertheless, the inferior conductivity of PBAs restricts the application in supercapacitors. In this work, nickel cobalt hexacyanoferrate (NiCoHCF) had been produced via a simple co-precipitation approach and coated with polypyrrole on its surface.

Novel multi-stimuli-responsive supramolecular gel based on quinoline for the fluorescence ultrasensitive detection of Feand Cu.

A novel gelator molecular based on quinolone (MN) has been successfully designed and synthesized. The gelator MN could self-assemble to form a supramolecular gel (OMN), which showed obvious aggregation-induced emission (AIE) in iso-Propyl alcohol (i-PrOH). Furthermore, the supramolecular organogel OMN realized ultrasensitive detection of Fe and Cu in aqueous medium and fluorescent quenching at 427 nm.

Prevalence and changes in depressive symptoms among postgraduate students: A systematic review and meta-analysis from 1980 to 2020.

Education actively helps us develop our well-being and health, but postgraduate students are at high risk of depression. The prevalence of depression symptoms varies from 6.2% to 84.

Reporting and methodological quality of COVID-19 systematic reviews needs to be improved: an evidence mapping.

Objectives: To assess the reporting and methodological quality of COVID-19 systematic reviews, and to analyze trends and gaps in the quality, clinical topics, author countries, and populations of the reviews using an evidence mapping approach.

Study Design And Setting: A structured search for systematic reviews concerning COVID-19 was performed using PubMed, Embase, Cochrane Library, Campbell Library, Web of Science, CBM, WanFang Data, CNKI, and CQVIP from inception until June 2020. The quality of each review was assessed using the Assessment of Multiple Systematic Reviews 2 (AMSTAR 2) checklist and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist.

Theoretical study of rhodium(III)-catalyzed synthesis of benzoxepine and coumarin.

The mechanisms of the rhodium-catalyzed cycloaddition of 2-vinylphenol with diphenylacetylene and carbon monoxide have been studied using density functional theory calculations at the B3LYP/6-31G (d, p) (Lanl2dz for Rh) level of theory. The SMD solvation model was used in MeCN solvents at M06-2X/6-311 ++ G (d, p) (Lanl2dz (f) for Rh) levels using a single-point calculation to consider the solvent effect. The calculation results show that there are two competitive reaction pathways for the cycloaddition reaction of rhodium-catalyzed synthesis of benzohexine and coumarin.

Palygorskite-anchored Pd complexes catalyze the coupling reactions of pyrimidin-2-yl sulfonates.

In this work, an anchored Pd complex (PGS-APTES-Pd(OAc)) was prepared simple and green steps from the natural clay mineral palygorskite and was well characterized by XPS, XRD, IR, SEM, and EDX. This complex was further utilized as a fine catalyst for the C-C/C-N coupling reactions of pyrimidin-2-yl sulfonates. Subsequently, the cyclic utilization test indicated the high stability and sustainability of this PGS-APTES-Pd(OAc) catalyst, and no activation was required in the recycling process, providing an applicable and reusable catalyst in organic synthesis.

Theoretical study on reaction mechanism of synthesis of iridium complexes having cyclometalated acyclic diaminocarbene ancillary ligands.

DFT calculations at the M06-2X level were performed to explore the reaction mechanism for the synthesis of the new cyclometalated iridium(III) complexes with acyclic diaminocarbene ancillary ligands. The solvent effects of the reaction systems have been considered by a single-point energy calculation using the SMD model in the experimental conditions of CHCl solvent. The calculated results show that the reaction consists of two main steps: the first step is the hydrogen transfer between the two N atoms, and the next step is the closed-loop process of the Ir atom and the aromatic ring ortho to release the HCl molecule.

Mechanistic study on the intramolecular oxa-[4 + 2] cycloaddition of substituted o-divinylbenzenes.

This paper reports a detailed computational study of the mechanisms of formation of oxacyclic derivatives from substituted o-divinylbenzenes by a photoinduced intramolecular oxa-[4 + 2] cycloaddition. The reaction mechanism and chemoselectivity of trans, trans- and cis, trans-substituted ortho-divinylbenzene were studied. Detailed density functional theory calculations show that the reaction system proceeds through two main steps: light-active intramolecular cyclization and Diels-Alder reactions of C=O.

Computational study of Ru-catalyzed cycloisomerization of 2-alkynylanilides.

The reaction mechanism of Ru-catalyzed cycloisomerization of 2-alkynylanilides to 3-substituted indole or 2-substituted indole was analyzed at the B3LYP level of density functional theory. The solvation effect of the system was also considered by SMD model. The calculation results show that the reaction system first forms a ruthenium π-alkyne complex.

Contamination levels and human health risk assessment of toxic heavy metals in street dust in an industrial city in Northwest China.

This study investigated the content, distribution, and contamination levels of toxic metals (Cd, Cr, Cu, Pb, and Zn) in street dust in Lanzhou, an industrial city in Northwest China. Meanwhile, the risk these metals posed to the urban ecosystem and human health was also evaluated using the potential ecological risk index and human exposure model. Results showed that concentrations of these metals in the dust are higher than the background value of local soil, with Cu having the highest levels.

[Effect of Biochar on Adsorption Behavior of Nonylphenol onto Loess Soil in Northwest China].

In the present study, nonylphenol (NP) was selected as the target pollutant to investigate the effect of biochar produced from wheat residue at different temperatures on loess soil based on the batch experiments. The research basically included adsorption kinetic, thermodynamic and some influencing factors such as biochar with different pyrolysis temperature, particle size and pH value. The results showed that the adsorption reaction of NP onto loess soil without biochar was 10 h during fast reaction, and after the addition of biochar into loess soil, the fast reaction time of NP adsorption was shortened.

Distribution, compositional pattern and sources of polycyclic aromatic hydrocarbons in urban soils of an industrial city, Lanzhou, China.

The level, distribution, compositional pattern and possible sources of polycyclic aromatic hydrocarbons (PAHs) in Lanzhou urban soil of Northwest China were investigated in this study. The total level of 22 PAHs ranged from 115 to 12,100 µg kg(-1) and that of 16 priority PAHs from 82.4 to 10,900 µg kg(-1).

Mechanism of the palladium-catalyzed hydrothiolation of alkynes to thioethers: a DFT study.

The mechanisms of the palladium-catalyzed hydrothiolation of alkynes with thiols were investigated using density functional theory at the B3LYP/6-31G(d, p) (SDD for Pd) level. Solvent effects on these reactions were explored using the polarizable continuum model (PCM) for the solvent tetrahydrofuran (THF). Markovnikov-type vinyl sulfides or cis-configured anti-Markovnikov-type products were formed by three possible pathways.

Covalently crosslinked fly ash/poly(acrylic acid-co-acrylamide) composite microgels as novel magnetic selective adsorbent for Pb²⁺ ion.

In order to improve the performance of treating waste-water with wastes, the magnetic fly ash (FA) particles were surface-modified with polymerizable groups as the crosslinker for the copolymerization with acrylic acid (AA) and acrylamide (AM) by a facile inverse suspension polymerization process, without any foreign organic crosslinker added. The optimized beadlike magnetic fly ash/poly(acrylic acid-co-acrylamide) composite microgels (FA/P(AA-AM)) with 3-dimensional crosslinking skeleton structure were selected as the magnetic selective microgel adsorbent for Pb(2+) ion, through a series of L(9)(3(4)) orthogonal experiments. It was found that the magnetic FA particles could improve the strength stability of the FA/P(AA-AM) composite microgels, also provide the ability of magnetic separation.