DFT rationalization of the mechanism and selectivity in a gold-catalyzed oxidative cyclization of diynones with alcohols.

The mechanism, regioselectivity, and chemoselectivity in a gold-catalyzed oxidative cyclization of diynones with alcohols to give furan-3-carboxylate derivatives were explored by density functional theory (DFT). The obtained results revealed that the first step of the global reaction involves a nucleophilic attack of a pyridine--oxide derivative on the catalyst-ligated diynone, forming a vinyl intermediate that can isomerize to an α,α'-dioxo gold carbene upon the cleavage of the N-O bond. In the second step, a nucleophilic addition is also completed pyridine--oxide instead of an alcohol proposed in the experiment.

DFT Study on the Mechanisms and Selectivities in Rh (III)-Catalyzed [5 + 1] Annulation of 2-Alkenylanilides and 2-Alkylphenols with Allenyl Acetates.

The mechanisms and regio-, chemo-, and stereoselectivity were theoretically investigated in the Rh(III)-catalyzed [5 + 1] annulation of 2-alkenylanilides and 2-alkylphenols with allenyl acetates. Two different reactants, 2-alkenylanilides and 2-alkylphenols, were selected as model systems in the density functional theory calculations. The obtained theoretical results show that both these reactants exhibit similar steps, namely, (1) N-H/O-H deprotonation and C-H activation, (2) allenyl acetate migratory insertion, (3) β-oxygen elimination, (4) intramolecular nucleophilic addition of the nitrogen/oxygen-rhodium bond resulting in [5 + 1]-annulation, and (5) protonation with the formation of the desired product and regeneration of the Rh(III) catalyst.

Theoretical Analysis of a Three-Component Reaction between Two Diazo Compounds and a Hydroxylamine Derivative: Mechanism, Enantioselectivity, and Effect of Cooperative Catalysis.

The mechanism, enantioselectivity, and effect of chiral phosphoric acid (CPA) cocatalyst were investigated by the density functional theory (DFT) for the three-component asymmetric aminohydroxylation between two diazo compounds and a hydroxylamine derivative. This type of cascade process is cooperatively catalyzed by Rh(OAc) and CPA. The obtained results clearly indicate that the first step of the global reaction involves a nucleophilic attack at the nitrogen center of -hydroxyaniline by rhodium-carbene intermediates producing imines.

Fabrication of Cellulose Filters Incorporating Metal-Organic Frameworks for Efficient Nicotine Adsorption from Cigarette Smoke.

To prevent negative effects of smoking, there is constant research on the development of various types of sustainable filter materials, capable of removing toxic compounds present in cigarette smoke. Because of the extraordinary porosity and adsorption properties, metal-organic frameworks (MOFs) represent promising adsorbents for volatile toxic molecules such as nicotine. This study reports new hybrid materials wherein six types of common MOFs of different porosity and particle size are incorporated into sustainable cellulose fiber from bamboo pulp, resulting in a series of cellulose filter samples abbreviated as MOF@CF.

Ratiometric Luminescent Thermometer Based on the Lanthanide Metal-Organic Frameworks by Thermal Curing.

The high-performance optical thermometer probes are of great significance in diverse areas; lanthanide metal-organic frameworks (Ln-MOFs) are a promising candidate for luminescence temperature sensing owing to their unique luminescence properties. However, Ln-MOFs have poor maneuverability and stability in complex environments due to the crystallization properties, which then hinder their application scope. In this work, the Tb-MOFs@TGIC composite was successfully prepared using simple covalent crosslinking through uncoordinated -NH or COOH on Tb-MOFs reacting with the epoxy groups on TGIC {Tb-MOFs = [Tb(atpt)(phen)(HO)]; Hatpt = 2-aminoterephthalic acid; phen = 1,10-phenanthroline monohydrate}.

Hybrid composites of lanthanide metal-organic frameworks with epoxy silanes for highly sensitive thermometry.

Post-synthetic modification of metal-organic frameworks (MOFs) and fabrication of hybrid composites are currently hot topics in the development of new functional materials. In this study, a facile and direct approach for coupling of lanthanide MOFs with epoxy silanes was developed, providing an access to a new series of functional composites. Two types of commercially available epoxy silane, namely 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECTMS) and (3-glycidoxypropyl)methyl diethoxysilane (KH563), were used to modify Ln-BTB MOFs ([Ln(BTB)(HO)]·2(CHO); Ln = Tb or EuTb; HBTB = 1,3,5-benzenetrisbenzoic acid) covalent grafting involving mechanical grinding, epoxide coupling and curing reactions.

DFT Rationalization of Gold(I)-Catalyzed Couplings between Alkynyl Thioether and Nitrenoid Derivatives: Mechanism, Selectivity Patterns, and Effects of Substituents.

The present work focuses on a theoretical investigation of mechanistic features, chemoselectivity, regioselectivity, and effect of substituents in the gold-catalyzed reactions of alkynyl thioethers and isoxazoles. The DFT calculations reveal that the nucleophilic attack of isoxazole to a βposition of catalyst-bound ynamide forms a vinyl intermediate. This undergoes cleavage of the N-O isoxazole bond and isomerizes to form an α-imino -sulfenyl gold carbene complex with stabilization of the Au-S interaction.

Safety, Tolerability and Pharmacokinetics of the Serotonin 5-HT6 Receptor Antagonist, HEC30654, in Healthy Chinese Subjects.

HEC30654 is a selective 5-HT6 receptor antagonist that was safe and well-tolerated in preclinical models of Alzheimer's disease. The objective of this double-blind, randomized, placebo-controlled clinical trial was to evaluate the safety, tolerability, and pharmacokinetic profile of HEC30654 after single ascending doses in healthy Chinese subjects. Healthy volunteers received a single oral dose of HEC30654 (5, 10, 15, 30, 60 mg).

Epoxy Functional Composites Based on Lanthanide Metal-Organic Frameworks for Luminescent Polymer Materials.

The integration of metal-organic frameworks (MOF) into organic polymers represents a direct and effective strategy for developing innovative composite materials that combine the exceptional properties of MOFs with the robustness of organic polymers. However, the preparation of MOF@polymer hybrid composites requires an efficient dispersion and interaction of MOF particles with polymer matrices, which remains a significant challenge. In this work, a new simple and direct approach was applied for the development of Ln-MOF@polymer materials.

DFT Study on Zr-Catalyzed Alkene Hydroaminoalkylation: Origin of Regioselectivity, Diastereoselectivity, and Influence of Substrate.

A DFT study was carried out to investigate a zirconium-catalyzed hydroaminoalkylation of alkenes with N-silylated benzylamine. A global reactivity index (GRI) analysis showed that that substrates act as electrophiles while the active zirconaaziridine behaves as a nucleophile. Furthermore, the distortion/interaction analysis unveiled the role of the distortion and interaction energies in controlling the regioselectivity and diastereoselectivity when different alkene substrates are used.

DFT Quest of the Active Species of the Gallium-Mediated Coupling of Methylidenemalonates and Acetylenes.

In this study, three different Ga-containing systems based on GaCl, GaCl, or ionic [Ga(L)][GaCl] (L = methylidenemalonate) complex were screened to elucidate the mechanism, regioselectivity, chemoselectivity, and role of Ga mediator in the reaction between two types of acetylenes (phenylacetylene and but-1-yn-1-ylbenzene) and methylidenemalonates, i.e., the 1,2-zwitterionic precursors that are similar to intermediates derived from donor-acceptor cyclopropanes (DACs).

Risk Factor Analysis and Risk Prediction Model Construction of Pressure Injury in Critically Ill Patients with Cancer: A Retrospective Cohort Study in China.

BACKGROUND The aim of this study was to analyze the risk factors of pressure injury (PI) in critically ill patients with cancer to build a risk prediction model for PI. MATERIAL AND METHODS Between January 2018 and December 2019, a total of 486 critically ill patients with cancer were enrolled in the study. Univariate analysis and binary logistic regression analysis were used to explore risk factors.

Carbocation versus Carbene Controlled Chemoselectivity: DFT Study on Gold- and Silver-Catalyzed Alkylation/Cyclopropanation of Indoles with Vinyl Diazoesters.

Density functional theory calculations were performed to investigate the catalyst-controlled selective functionalization of indoles with vinyl diazoacetates. The detailed reaction mechanism was established, and different roles of carboncation or carbene intermediates in defining an experimentally observed chemo- and regioselectivity were fully rationalized.

Computational Exploration of Counterion Effects in Gold(I)-Catalyzed Cycloisomerization of -(Alkynyl)styrenes.

A detailed theoretical analysis of the mechanism and chemoselectivity for gold(I)-catalyzed reaction of -(alkynyl)styrene containing an isopropyl and a methyl at the terminal position of the alkene has been reported in this work. Two different counterions (SbF and OTs) were studied as model catalysts. According to our calculation, for SbF , the reaction pathway is more prone to direct 1,2-H shifts (isopropyl H) than the elimination and ring expansion pathway.

Function-Oriented: The Construction of Lanthanide MOF Luminescent Sensors Containing Dual-Function Urea Hydrogen-Bond Sites for Efficient Detection of Picric Acid.

Two novel lanthanide metal-organic framework (Ln-MOF) luminescent sensors for the detection of picric acid have been successfully assembled. Following a function-oriented strategy, urea hydrogen-bonding functional sites were introduced into two MOF frameworks. A structural analysis indicated that the two MOFs have the exact same structure, namely 2D layers with diamond-shaped holes that are accumulated into a 3D framework through the hydrogen-bonding interactions between urea and carboxylate groups.

Multifunctional Ln-MOF Luminescent Probe for Efficient Sensing of Fe, Ce, and Acetone.

A new series of five three-dimensional Ln(III) metal-organic frameworks (MOFs) formulated as [Ln(μ-L)(μ-HCOO)(μ-OH)(μ-O)(DMF)(HO)] {Ln = Tb (1), Eu (2), Gd (3), Dy (4), and Er (5)} was successfully obtained via a solvothermal reaction between the corresponding lanthanide(III) nitrates and 2-(6-carboxypyridin-3-yl)terephthalic acid (HL). All of the obtained compounds were fully characterized, and their structures were established by single-crystal X-ray diffraction. All products are isostructural and possess porous 3D networks of the fluorite topological type, which are driven by the cubane-like [Ln(μ-OH)(μ-O)(μ-HCOO)] blocks and μ-L spacers.

Novel double layer lanthanide metal-organic networks for sensing applications.

A trifunctional aromatic building block (HL) containing three different types of functional groups (carboxyl C([double bond, length as m-dash]O)OH, aldehyde C([double bond, length as m-dash]O)H, and O-ether) was applied for the hydrothermal synthesis of two novel lanthanide 2D coordination polymers [Ln(μ-HL)(μ-L)(phen)] {Ln = Tb (1) and Eu (2); HL = 5-methoxy-(4-benzaldehyde)-1,3-benzene dicarboxylic acid; phen = 1,10-phenanthroline}. Both compounds 1 and 2 are isostructural and reveal very complicated 2D metal-organic double layers with the 3,4L27 topology. The presence of free aldehyde groups positioned outside of the double layers opens up a possibility of using them as functional groups toward sensing amines and small organic molecules.

New lanthanide(iii) coordination polymers: synthesis, structural features, and catalytic activity in CO fixation.

A new series of lanthanide coordination polymers formulated as [Ln(μ-L)(μ-L)(HO)]X (Ln/X = Er/Cl (1), Er/Br (2), Tm/Cl (3), Tm/Br (4), Yb/Cl (5), and Yb/Br (6); L = 1,3-bis(4-carboxyphenyl) imidazolium carboxylate(1+)) were solvothermally generated and fully characterized. Single-crystal X-ray diffraction analysis shows that all products possess isomorphous structures that are composed of cationic 1D double chains with encapsulated halide anions. From a topological perspective, such 1D chains can be classified as a binodal 3,5-connected net with a unique topology defined by the point symbol of (3·4)(3·4·5·6·7).

Hybrid materials based on novel 2D lanthanide coordination polymers covalently bonded to amine-modified SBA-15 and MCM-41: assembly, characterization, structural features, thermal and luminescence properties.

Three novel 2D coordination polymers [Tb(μ-L)(μ-HL)(μ-HCOO)(DEF)] (Tb-L), [Eu(μ-L)(L)(HO)] (Eu-L), and [Nd(μ-L)(L)(HO)] (Nd-L) were assembled from the corresponding lanthanide(iii) nitrates and 5 methoxy-(4-benzaldehyde)-1,3-benzenedicarboxylic acid (HL) as a main multifunctional building block bearing carboxylate and aldehyde functional groups, using HO/DEF {DEF = N,N-diethylformamide} as a reaction medium. The obtained coordination polymers were isolated as stable microcrystalline solids and fully characterized by elemental analysis, FT-IR spectroscopy, TGA, BET, PXRD, and single-crystal X-ray diffraction methods. Their structures feature intricate 2D metal-organic networks, which were topologically classified as underlying layers with the 4,6L26 (for Tb-L) or sql (for Eu-L and Nd-L) topologies.

A Multi-responsive Regenerable Europium-Organic Framework Luminescent Sensor for Fe , Cr Anions, and Picric Acid.

A novel luminescent microporous lanthanide metal-organic framework (Ln-MOF) based on a urea-containing ligand has been successfully assembled. Structural analysis revealed that the framework features two types of 1D channels, with urea N-H bonds projecting into the pores. Luminescence studies have revealed that the Ln-MOF exhibits high sensitivity, good selectivity, and a fast luminescence quenching response towards Fe , Cr anions, and picric acid.

Pt@UiO-66 heterostructures for highly selective detection of hydrogen peroxide with an extended linear range.

In this study, a good core-shell heterostructure of Pt NPs@UiO-66 was fabricated by encapsulating presynthesized platinum nanoparticles (Pt NPs) into the host matrix of UiO-66 which possesses the slender triangular windows with a diameter of 6 Å. The transmission electron microscopy images exhibited that the number of the encapsulated Pt NPs and the crystalline morphology of as-synthesized core-shell heterostructure samples had a series of changes with increasing the volume of the injected Pt NPs precursor solution. Among these samples, the Pt NPs@UiO-66-2 sample had a good crystalline morphology with several well-dispersed Pt NPs encapsulated in UiO-66 frameworks.

Water-soluble colorimetric and ratiometric fluorescent probe for selective imaging of palladium species in living cells.

A novel water-soluble colorimetric and ratiometric fluorescent probe was synthesized and applied to imaging palladium species under physiological conditions in phosphate buffered saline (PBS) containing less than 1% organic cosolvent without adding any additional reagents. Based on palladium triggered terminal propargyl ethers cleavage reaction, the probe exhibited a high selectivity and sensitivity for palladium species of all the typical oxidation states (0, +2, +4), with a low detection limit (25 nM, 2.7 μg/L) and an obvious color change.

A highly selective two-photon fluorescent probe for detection of cadmium(II) based on intramolecular electron transfer and its imaging in living cells.

A new quinoline-based probe was designed that shows one-photon ratiometric and two-photon off-on changes upon detecting Cd(2+) . It exhibits fluorescence emission at 407 nm originating from quinoline groups in Tris-HCl (25 mM, pH 7.40), H2 O/EtOH (8:2, v/v).