Anionic Sites Research Articles

Covalent Stabilization of the Iridium-Containing Oxyhydrides Sr2Mn0.5Ir0.5O3.25H0.75 and Sr2Mn0.5Ir0.5O2.66H1.33.

Reaction between Sr2Mn0.5Ir0.5O4 and CaH2 or LiH yields the iridium-containing oxyhydride phases Sr2Mn0.5Ir0.5O3.25H0.75 or Sr2Mn0.5Ir0.5O2.66H1.33, respectively. Analysis of Mn K-edge XANES data indicate the presence of Ir3+ centers in these oxyhydride phases, whose low-spin d6 configuration is consistent with the "covalent stabilization" of the metastable oxyhydride phases, as seen previously in analogous ruthenium and rhodium containing materials. Neutron powder diffraction data indicate the hydride ions are located exclusively within the "equatorial" anion sites of Sr2Mn0.5Ir0.5O3.25H0.75. In contrast, hydride ions are observed on both the equatorial and axial anion sites of Sr2Mn0.5Ir0.5O2.66H1.33. This highly unusual anion distribution is attributed to a combination of the strong trans-influence of Ir-H σ-bonds and the stabilization of fac-IrO3H3 centers by spin-orbit coupling effects. Magnetization data indicate that Sr2Mn0.5Ir0.5O4 and Sr2Mn0.5Ir0.5O3.25H0.75 adopt spin glass states at low temperature, behavior which is attributable to the cation disorder in Sr2Mn0.5Ir0.5O4 and the cation and anion disorder in Sr2Mn0.5Ir0.5O3.25H0.75. In contrast, magnetization data collected from Sr2Mn0.5Ir0.5O2.66H1.33 show no evidence of any magnetic phase transition down to 5 K, consistent with the dilution of the magnetic network by the introduction of diamagnetic Ir3+ on the formation of the oxyhydride phase.

Misfit Layered Compounds: Insights into Chemical, Kinetic, and Thermodynamic Stability of Nanophases.

ConspectusCompounds with layered structures (2D-materials), like transition metal-dichalcogenides (e.g., MoS2), attracted a great deal of interest in the scientific community in recent years. This interest can be attributed to their unique lamellar structure, which induces large anisotropy in their physicochemical properties. Furthermore, owing to the weak van der Waals interaction between the layers, they can be cleaved along the a-b plane, which allows fabricating single layers with physical properties entirely different from the bulk material. Moreover, stacking layers of different 2D-materials on top of each other has led to a wealth of new observations, for instance, by twisting two layers with respect to each other and producing Moiré lattice. Another outstanding property of inorganic layer compounds is their tendency to form nanotubes, reported first (for WS2) many years ago and subsequently from many other layered compounds.Among the 2D-materials, misfit layer compounds make a special class with an incommensurate and nonstoichiometric lattice made of an alternating layer with rocksalt structure, like LaS (O) and a layer with hexagonal structure, like TaS2 (T). The lack of lattice commensuration between the two slabs leads to a built-in strain, which can be relaxed via bending. Consequently, nanotubes have been produced from numerous MLC compounds over the past decade and their structure was elucidated.Owing to their large surface area, nanostructures are generally metastable and tend to recrystallize into microscopic crystallites via different mechanisms, like Ostwald ripening, or chemically decompose and then recrystallize. The stability of nanostructures at elevated temperatures has been investigated quite scarcely so far. In this perspective, electron microscopy as well as synchrotron-based X-ray absorption and reflection techniques were used to elucidate the chemical selectivity and decomposition routes of rare-earth based MLC nanotubes prepared at elevated temperatures (800-1200 °C).As for the chemical selectivity, entropic effects are expected to dictate the random distribution of the chalcogen atoms on the anion sites of the MLC nanotubes at elevated temperatures. Nonetheless, the sulfur atoms were found to bind exclusively to the rare-earth atom (Ln = La, Sm) of the rocksalt slab and the selenium to the tantalum of the hexagonal TX2 slab. This uncommon selectivity was not found in other kinds of nanotubes like WSe2xS2(1-x). In other series of experiments, the lack of utter symmetry in the multiwall nanotubes leads to exclusions of certain X-ray (0kl) reflections, which was used to distinguish them from the bulk crystallites. The transformation of Ln-based MLC nanotubes into microscopic flakes was followed as a function of the synthesis temperature (800-1200 °C) and the synthesis time (1-96 h). Furthermore, sequential high-temperature transformations of the (O-T) lattice into (O-T-T) and finally (O-T-T-T) phases via deintercalation of the LnS slab was observed. This autocatalytic process is reminiscent of the deintercalation of alkali atoms from different layered structure materials. Annealing at higher temperatures and for longer periods of time eventually leads to the decomposition of the ternary MLC into binary metal-sulfide phases, as well as partial oxidation of the product. This study sheds light on the complex mechanism of high-temperature chemical stability of the nanostructures.

Highly effective fluorescence detection of UO22+ ions by an anionic Na/Eu heterometallic metal–organic framework with Lewis basic chelating sites

Uranium is a serious radioactive contaminant that can easily migrate into groundwater and surface water, posing a deadly threat to human health. Despite the development of various materials for detecting uranyl ions in water, rational design and synthesis of new uranium sensors with sensitivity, selectivity, and fast response remain challenging. Herein, we demonstrate a novel strategy for obtaining highly sensitive and selective UO22+ sensors by constructing heterometallic metal–organic framework with both an anionic skeleton and abundant chelating sites. Namely, the first anionic Na/Eu heterometallic metal–organic framework (Na/Eu-MOF) based UO22+ sensor is successfully synthesized by using sodium salt and europium salt as reactants, and abundant ether groups were introduced into its porous structure as chelating Lewis basic sites. Beneficial from the synergistic effect between the anionic skeleton and the chelating sites, Na/Eu-MOF achieved rapid, selective adsorption and fluorescence quenching toward uranyl ion. The detection limits of Na/Eu-MOF in deionized and lake water were determined to be 49.7 nM and 113.0 nM, respectively, which are lower than the maximum concentration of 130.0 nM in drinking water proposed by the United States Environmental Protection Agency, indicating potential environmental applications. The detection capability of Na/Eu-MOF is attributed to the combination system of energy competition and interactions between UO22+ ions and Na/Eu-MOF. This work offers a feasible strategy to construct an anionic heterometallic metal–organic framework with chelating sites for uranyl detection in an aqueous solution.

Mechanistic study of β-Ga2O3 nitridation by RF nitrogen plasma for GaN heteroepitaxy

The transformation of 2¯01β-Ga2O3 to h-GaN under exposure to RF nitrogen plasma was monitored in situ by reflection high-energy electron diffraction. Analysis of the reaction kinetics reveals that the nitridation process is initiated by the formation of an oxynitride phase and proceeds via two-dimensional nucleation and growth of wurtzite GaN grains. X-ray photoelectron spectra suggest a Ga−(NxO1−x) type configuration dominates the surface early in the nitridation process. The surface restructuring is followed by a diffusion-fed phase transformation, which propagates the wurzite GaN structure into the substrate upon reaching 70% nitrogen anion site occupation, corresponding to the oxygen solubility in h-GaN. A direct correlation is observed between the nitridated film morphology and the epitaxial film crystallinity, demonstrating control of the residual strain, lateral coherence, and mosaicity in subsequent GaN epitaxy by the nitridation conditions. This study provides mechanistic details of the nitridation reaction of 2¯01β-Ga2O3 facilitating the optimization of the nitridation process toward improving GaN-2¯01β-Ga2O3 heterojunctions.

Modeling of the metal–insulator transition temperature in alio-valently doped VO2 through symbolic regression

The correlated semiconductor vanadium dioxide (VO2) exhibits an insulator–metal transition (IMT) near room temperature, which is of interest in various device applications. Precise IMT temperature control is crucial to determine the use cases across technologies such as thermochromic windows, actuators for robots or neuronal oscillators. Doping the cation or anion sites can modulate the IMT by several tens of degrees and control hysteresis. However, modeling the effects of control parameters (e.g., doping concentration, type of dopants) is challenging due to complex experimental procedures and limited data, hindering the use of traditional data-driven machine learning approaches. Symbolic regression (SR) can bridge this gap by identifying nonlinear expressions connecting key input parameters to target properties, even with small data sets. In this work, we develop SR models to capture the IMT trends in VO2 influenced by different dopant parameters. Using experimental data from the literature, our study reveals a dual nature of the IMT temperature with varying tungsten (W) doping concentrations. The symbolic model captures data trends and accounts for experimental variability, providing a complementary approach to first-principles calculations. Our feature-driven analysis across a broader class of dopants informs selectivity and provides qualitative insights into tuning phase transition properties valuable for neuromorphic computing and thermochromic windows.

Effect of lithium concentration on the network connectivity of nuclear waste glasses

Structure of borosilicate glasses with varying Li2O contents were investigated using Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR), employing 6Li, 11B, 23Na, 27Al and 29Si nuclei. 11B MAS NMR revealed that increasing Li2O contents result in formation of [BO4]− sites at the expense of BO3. 11B{6Li} and 27Al{6Li} dipolar heteronuclear multiple quantum correlation (D-HMQC) NMR revealed Li as a charge compensator for anionic tetrahedral sites with increased Li. 11B{6Li} J-coupling mediated HMQC NMR suggested the possible association of Li with non-bridging oxygens on Q2 and Q3 sites, indicating its dual role in the glass network. 29Si and 23Na MAS NMR spectra showed depolymerisation of the silicate network and shortening of Na-O bond lengths with increased Li. NMR results are supported by Raman spectroscopy and thermal analysis that indicate depolymerisation of the silicate network and a reduction in glass transition temperature at higher Li content.

Naphthyl-functionalized acetamide derivatives: Promising agents for cholinesterase inhibition and antioxidant therapy in Alzheimer’s disease

This study presents the synthesis and characterization of a series of 13 novel acetamides. These were subjected to Ellman’s assay to determine the efficacy of the AChE and BChE inhibitors. Finally, we report their antioxidant activity as an alternative approach for the search for drugs to treat AD. These studies revealed that compounds 1a–1k and 2l–2m were obtained in moderate yield. Four amides (1h, 1j, 1k, and 2l) were selective for one of the enzymes (BChE); thus, those that inhibited BChE were more active than the positive control (galantamine) and showed better IC50 values (3.30–5.03 µM). The theoretical free binding energies calculated by MM-GBSA indicated that all inhibitors were more stable than rivastigmine, and the inhibition mechanisms involved the entire active site: peripheral anionic site, oxyanion hole, acyl-binding pockets, and catalytic site. We examined the cytotoxicity of compounds 1h, 1j, 1k, and 2l in human dermal cells and found that they did not exhibit any toxic effects under the tested conditions. Additionally, these compounds, which also inhibited BChE, displayed mixed inhibition and did not exhibit hemolytic effects on human erythrocytes. Furthermore, the ABTS and DPPH assays indicated that, although none of the compounds showed activity in the DPPH assay, the EC50 values for radical trapping by the ABTS method showed that compounds 1a, 1d, 1e, and 1g had EC50 values lower than 10 µg/mL, indicating their strong radical scavenging capacity. We also report the crystal structures of compounds 1c, 1d, 1f, and 1g, which are found in monoclinic crystal systems.

Site Disorder Drives Cyanide Dynamics and Fast Ion Transport in Li6PS5CN.

Halide argyrodite solid-state electrolytes of the general formula Li6PS5 X exhibit complex static and dynamic disorder that plays a crucial role in ion transport processes. Here, we unravel the rich interplay between site disorder and dynamics in the plastic crystal argyrodite Li6PS5CN and the impact on ion diffusion processes through a suite of experimental and computational methodologies, including temperature-dependent synchrotron powder X-ray diffraction, AC electrochemical impedance spectroscopy, 7Li solid-state NMR, and machine learning-assisted molecular dynamics simulations. Sulfide and (pseudo)halide site disorder between the two anion sublattices unilaterally improves long-range lithium diffusion irrespective of the (pseudo)halide identity, which demonstrates the importance of site disorder in dictating bulk ionic conductivity in the argyrodite family. Furthermore, we find that anion site disorder modulates the presence and time scales of cyanide rotational dynamics. Ordered configurations of anions enable fast, quasi-free rotations of cyanides that occur on time scales of 1011 Hz at T = 300 K. In contrast, we find that cyanide dynamics are slow or frozen in Li6PS5CN when site disorder between the cyanide and sulfide sublattices is present at T = 300 K. We rationalize the observed differences in cyanide dynamics in the context of elastic dipole interactions between neighboring cyanide anions and local strain induced by the configurations of site disorder that may impact the energetic landscape for cyanide rotational dynamics. Through this study, we find that anion disorder plays a decisive role in dictating the extent and time scales of both lithium ion and cyanide dynamics in Li6PS5CN.

Some heterocycles connected to substituted piperazine by 1,3,4-oxadiazole linker: Design, synthesis, anticholinesterase and antioxidant activity

AD is a multifactorial neurodegenerative disease that has caused morbidity and mortality on a global scale. Currently, there are only a few drugs used in the treatment of AD. Although many compounds that aim at new targets have reached clinical trials, none have been approved. However, discovering efficient drugs for AD treatment is one of the biggest challenges for pharmaceutical research and requires strong support. In this paper, we aim to design a series of indole, benzothiophene, and thiophene bearing 1,3,4-oxadiazole linker to the piperazine basic center and evaluate for their antioxidant and inhibitory activity against both cholinesterase enzymes. Among the compounds, 6a, 7b, and 8b exhibited moderate cationic radical scavenging activities with IC50 values ranging from 20.39 to 30.10 μM. The inhibitory activity results revealed that compounds 5c (IC50 for AChE = 53.91 μM and for BChE = 55.81 μM) and 6c (IC50 for AChE = 54.42 μM and BChE = 45.82 μM) bearing 2-fluorophenyl piperazine moiety showed both AChE and BChE inhibition with moderate IC50 values. To explore the binding properties of the target compounds into the active site of the enzyme, a molecular docking study was carried out using MOE software. The docking study showed that compound 6c targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE/BChE and formed important interactions with key residues. Moreover, theoretical physicochemical properties of the best active compound 6c were calculated by the SwissADME web service. It obeyed Lipinski's rule of five and had high GI absorption (gastrointestinal absorption) and good permeating to the blood-brain barrier (BBB). The compound 6c can be considered a promising compound and provides us directions for further research of anti-AD agent development.

Molecular docking studies and in-vitro cholinesterase inhibitory activities of chemical constituents of Calophyllum gracilentum

Calophyllum species are well known due to their abundance of potentially beneficial phytochemicals, such as xanthones, coumarins, and others. However, Calophyllum gracilentum is an understudied specie with very limited information. Medicinal plants have been proven to have therapeutic potential in managing neurological disorders associated with acetylcholinesterase (AChE) dysregulation. Still, there has been little investigation on Calophyllum plants for this purpose. Herein, we report on the isolation of a new oxygenated xanthone 5,10-dihydroxy-9-methoxy-2,2-dimethyl-12-(3-methylbut-2-enyl) pyrano[3,2-b] xanthen-6(2 H)-one (1) and eleven known xanthones (2–12), three chromanone acids (13–15), and phytosterols (16–18), respectively from the stem bark of the Calophyllum gracilentum. The evaluation of AChE inhibitory activity showed that all the extracts and xanthones (2, 5, 6, 8, 9, 12) tested have potential AChE inhibitory activity. Compounds (5) and (12) are prospective AChE inhibitors with IC50 values of 1.8 ± 0.0001 and 4.0 ± 0.0002 µmol/L. The molecular docking analysis demonstrated compound (5) and compound (12) bind well to the active site which is the anionic site containing Trp 84 and Asp 72 in the of Torpedo californica acetylcholinesterase (TcAChE) through π-π stacking, hydrogen bonding, and π-donor hydrogen bond from the xanthone ring, besides π-alkyl and π-σ interactions from the substituent group with the binding energy of −11.1 kcal/mol for compound (5) and binding energy of −10.4 kcal/mol for compound (12).

Zwitterionic adsorbents derived from self-Exfoliated ionic covalent organic frameworks for efficient Co-Removal of anionic and cationic radionuclides

Exfoliating Covalent Organic Frameworks (COFs) into few-layer or even monolayer nanosheets not only improves the exposure of active sites and facilitates mass transfer efficiency, but also enhances their solubility or dispersion to achieve solution processability. As the Coulomb repulsion can weaken the stacking interactions, the construction of ionic COFs shows promising prospects for obtaining self-stripping nanosheets, but precisely controlling the self-exfoliated degree remains a challenge. Herein, we found for the first time that varying the number of hydroxyl groups in the building blocks could significantly affect the self-exfoliated degree for ionic COFs, and thus successfully produced a series of ionic COFs with stepwise solubility differences. Interestingly, the trend of self-exfoliated degree and solubility of cationic (EBCOFs) and anionic COFs (SDCOFs) were completely opposite to each other. Mechanistic studies indicated that more hydroxyl groups as electron donating groups increased the electron density of ionic COFs, resulting in a decrease in the Coulomb repulsion of cationic COFs (EBCOFs) but an increase in the Coulomb repulsion of anionic COFs (SDCOFs). Furthermore, in order to achieve the efficient co-removal of anionic and cationic radionuclides, we assembled cationic and anionic COF nanosheets through electrostatic attraction to obtain a novel zwitterionic COF (EB@SD COF) with both anion and cation adsorption sites. Impressively, EB@SD COF demonstrated rapid and efficient co-adsorption of ReO4- (a substitute for TcO4-) and Sr2+ with the maximum adsorption capacities of 117.6 and 122.4 mg/g, respectively. This work not only developed an effective zwitterionic COF adsorbent for the co-removal of radionuclides but also broadened the horizon of preparation methods for self-exfoliated ionic COFs.

Printed potentiometric, non-enzymatic sensors based on Zr(IV)-porphyrins for determination of lactate

The feasibility of using Zr-porphyrins as ionophores selective towards lactate ions was examined. Zr-tetraphenylporphyrin (Zr-TPP) and Zr-octaethylporphyrin (Zr-OEP) were tested in polyurethane membranes plasticized with dioctyl sebacate or o-nitrophenyl ether and containing cationic or anionic lipophilic sites, respectively. The best lactate response characteristics were registered for membrane plasticized with dioctyl sebacate and doped with Zr-TPP and cationic lipophilic sites. Classical electrodes with this membrane showed high selectivity towards lactate ions with a sensitivity of −76.6 mV dec−1 and linear lactate calibration range from 10−4 M to 10−1 M. Polymeric membranes containing Zr-TPP were then drop-casted on screen-printed transducers with electrodes made of graphene-containing paste. It was found that the potentiometric behavior of these miniature planar sensors is very similar to classical electrodes. In the next step, fully printed sensors, with both graphene electrodes and ion-selective polymeric membranes, were fabricated using aerosol jet printing. The sensitivity of these electrodes towards lactate was −79.01±0.39 mV dec−1 with a linear response range from 10−3.5 M to 10−1 M and a fast response to lactate concentration changes. The proposed electrode demonstrates a rare example of a potentiometric, non-enzymatic sensor for the determination of lactate ions, with the possibility of miniaturization and mass fabrication using printing methods.

Investigating the Synthesis Pathway of a Disordered Rocksalt Phase Via in Situ X-Ray Characterization

Recently, Li-rich disordered rocksalt (DRX) materials have gathered a lot of attention as prospective Li-ion battery cathode materials owing to their high electrochemical storage capacity and high specific energy. In contrast to the current commercialized layered Li-ion battery cathode materials (e.g. LiCoO2, LiNixMnyCo1-x-yO2), which contain toxic and expensive metals, DRX can accommodate a large variety of transition metals, such as Mn and Ti, which are cheap and earth abundant. These characteristics make them a cheaper and a more sustainable alternative to the current commonly used layered cathodes.Unlike the commercial Li-ion battery cathodes, where the transition metals and the Li are arranged in an ordered manner, DRX exhibits a highly disordered cation framework. Fluorine incorporation into DRX was extensively studied, where the fluorine anions are distributed disorderly at the anion sites. Previous studies have shown that the electrochemical performance of DRX cathodes can be enhanced via fluorination, as fluorine can effectively suppress the oxygen redox activity observed in many Li-rich cathodes. However, a large degree of fluorine incorporation into DRX was found to be difficult. As a result, it is important to study the mechanism in which fluorine is incorporated into the structure, and the role of LiF during synthesis of DRX.In addition to fluorination, the degree and type of short-range cation ordering (SRO) presenting in the materials were also found to have a significant impact on the electrochemical performance of DRX materials. The SRO present can be modified with synthesis techniques, where samples annealed at the synthesis temperature for a longer period exhibit a higher degree of SRO. This observation has demonstrated that the synthesis conditions and SRO are highly correlated. It is hence possible to control the SRO in DRX materials via varying synthesis conditions, thereby enhancing their electrochemical performance. Keeping this in mind, it is hence important to understand the mechanism by which DRX is formed.In this work, we have performed in situ synchrotron X-ray diffraction monitoring the phase progression during the solid-state synthesis of Li1.1Mn0.8Ti0.1O1.9F0.1 DRX oxyfluoride. We have observed several crystalline intermediate phases emerged before the formation of the DRX phase. Coupled with X-ray absorption spectroscopy, we are able to gain additional insights into the intermediate phases formed during the synthesis. This poster will describe the investigation of the synthesis pathway of Li1.1Mn0.8Ti0.1O1.9F0.1 DRX oxyfluoride using X-ray characterization techniques. The formation mechanism of this DRX phase will also be discussed.

Secondary metabolites in Cordyceps javanica with insecticidal potential

Cordyceps javanica has been registered as a fungal insecticide in several countries. However, little is known about whether metabolic toxins are involved in the insecticidal process. In this research, we assessed the insecticidal activity of the fermentation broth of C. javanica. Myzus persicae mortality differed when exposed to the metabolized C. javanica broths at 3 days post fermentation (DPF) and 5 DPF. Comparison of the metabolic fluid at 3 DPF and 5 DPF revealed a key alkaloid, heteratisine, which was found to have insecticidal activity and acetylcholinesterase (AChE) inhibitory activity. Heteratisine has high insecticidal activity against adult M. persicae, the absolute 50% lethal concentration (LC50) was only 0.2272 mg/L. Heteratisine showed high inhibitory activity on AChE with the 50% maximal inhibitory concentration (IC50) of 76.69 μM. Molecular docking and dynamic simulations showed that heteratisine conjugation occurs at the peripheral anionic site (PAS) of the AChE of M. persicae, leading to suppression of enzyme activity. Heteratisine was rarely found in fungal metabolites, which helps us to understand the complex and elaborate insecticidal mechanism of C. javanica.

Low-Molecular Weight Branched Polyethylenimine Reduces Cytokine Secretion from Human Immune System Monocytes Stimulated with Bacterial and Fungal PAMPs.

The innate immune system is an evolutionarily conserved pathogen recognition mechanism that serves as the first line of defense against tissue damage or pathogen invasion. Unlike the adaptive immunity that recruits T-cells and specific antibodies against antigens, innate immune cells express pathogen recognition receptors (PRRs) that can detect various pathogen-associated molecular patterns (PAMPs) released by invading pathogens. Microbial molecular patterns, such as lipopolysaccharide (LPS) from Gram-negative bacteria, trigger signaling cascades in the host that result in the production of pro-inflammatory cytokines. LPS stimulation produces a strong immune response and excessive LPS signaling leads to dysregulation of the immune response. However, dysregulated inflammatory response during wound healing often results in chronic non-healing wounds that are difficult to control. In this work, we present data demonstrating partial neutralization of anionic LPS molecules using cationic branched polyethylenimine (BPEI). The anionic sites on the LPS molecules from Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) are the lipid A moiety and BPEI binding create steric factors that hinder the binding of PRR signaling co-factors. This reduces the production of pro-inflammatory TNF-α cytokines. However, the anionic sites of Pseudomonas aeruginosa (P. aeruginosa) LPS are in the O-antigen region and subsequent BPEI binding slightly reduces TNF-α cytokine production. Fortunately, BPEI can reduce TNF-α cytokine expression in response to stimulation by intact P. aeruginosa bacterial cells and fungal zymosan PAMPs. Thus low-molecular weight (600 Da) BPEI may be able to counter dysregulated inflammation in chronic wounds and promote successful repair following tissue injury.

Synthesis and Biological Evaluation of Colchicine─Aryl/Alkyl Amine Hybrids as Potential Noncytotoxic Cholinesterase Inhibitors: Identification of SBN-284 as a Dual Inhibitor of Cholinesterases and NLRP3 Inflammasome.

Colchicine, one of the oldest anti-inflammatory natural products still used clinically, inhibits NF-κB signaling and NLRP3 inflammasome activation. Despite its cytotoxicity and narrow therapeutic range, colchicine continues to intrigue medicinal chemists exploring its anti-inflammatory potential. This study aimed to investigate the colchicine scaffold for its role in Alzheimer's disease by targeting neuroinflammation and cholinesterases. Molecular docking revealed that colchicine's hydrophobic trimethoxyphenyl framework can potentially bind to the peripheral anionic site of cholinesterases. Hybrid structures combining colchicine with aryl/alkyl amines were designed to bind both peripheral and catalytic sites of cholinesterases. We describe here the design, synthesis, and in vitro cytotoxicity evaluation of these colchicine-aryl/alkyl amine hybrids, along with their in silico interactions with the cholinesterase active site gorge. Nontoxic analogs demonstrating strong cholinesterase binding affinity were further evaluated for their anticholinesterase and antineuroinflammatory activities. The colchicine-donepezil hybrid, SBN-284 (3x), inhibited both acetylcholinesterase and butyrylcholinesterase as well as the NLRP3 inflammasome complex at low micromolar concentrations. It achieved this through noncompetitive inhibition, occupying the active site gorge and interacting with both peripheral and catalytic anionic sites of cholinesterases. Analog 3x was shown to cross the blood-brain barrier and exhibited no toxicity to neuronal cells, primary macrophages, or epithelial fR2 cells. These findings highlight the potential of this lead compound for further preclinical investigation as a promising anti-Alzheimer agent.

Hierarchical multi-interface Co1-xS/Co9S8@C hollow microsphere for enhancing dielectric polarization as an efficient microwave absorber

Recently, close attention has been devoted to exploring highly efficient microwave absorbing materials (MAMs). Owing to their tunable dielectric properties and controllable structure, materials doped with heteroatoms have been regarded as promising absorbers. Herein, the Co@C, CoSe2@C, and hierarchical Co1-xS/Co9S8@C hollow microspheres were prepared using hydrothermal and subsequent carbonization, selenium, and vulcanization processes, respectively. The existence of anionic sites immensely affects the permittivity and conductivity of a composite. As a result, CoSe2@C and Co1-xS/Co9S8@C hollow microspheres showed improved conductivity and dielectric losses. Particularly, due to the multiphase transformation in the vulcanization process, the Co1-xS/Co9S8@C hollow microsphere possessed numerous heterogeneous interfaces and rich lattice defects, which led to local electronic redistribution and reinforced dielectric polarization. It exhibited a minimum reflection loss (RLmin) of −61.0 dB at a thinner thickness of 2.0 mm. This study contributes to the insight into the polarization loss mechanisms of multi-component and heteroatom doping composites and stimulates the design of high-efficiency MAMs.

Influence of anions on the structural and catalytic properties of CTA-MCM-41

CTA-MCM-41 — Mobil Composition of Matter 41 with cetyltrimethylammonium cations (CTA+) — is a hybrid silica known for its high basic catalytic activity due to anionic silanolate sites (Si−O-) that are bound to CTA+. The synthesis of this material depends on the properties of CTA+ micelles in aqueous dispersion which, in turn, depend on the surrounding anions. Thus, this study investigated different types and amounts of anions in the synthesis of CTA-MCM-41. Chloride (Cl-), bromide (Br-), iodide (I-), nitrate (NO3-) and hydroxide (OH-) anions in sodium form were added to the synthesis mixture, and the obtained silicas were tested in the transesterification reaction. It is hereby presented a comprehensive study on how micelles-anion interfaces play a key role in the synthesis of this important hybrid silica catalyst, and it was possible to synthesize a more active basic catalyst than the conventional CTA-MCM-41, just by exploring such surface chemistry effects. Three significant features are highlighted: (1) improved catalytic activity of CTA-MCM-41 applied in transesterification; (2) Synthesis of CTA-MCM-41 with higher retention of cations per silica and higher amount of silanolate basic sites; (3) deepening knowledge of the synthesis mechanism of materials from the MCM-41 family. The effects are more pronounced in the order I- > NO3- > Cl-, in accordance with the Hofmeister ion series. Hydroxide anions, however, led to the greatest increase in the number of sites and basic catalytic activity (up to 52.4 %). These results reinforce the validity of the {S+, X-, I-} (S: surfactant; X: anion; I: silica) silica formation mechanism and reveal a synthesis with hydroxide anions that produces a catalyst more active than conventional CTA-MCM-41.

Synthesis, crystal and electronic structures of two novel tunnel bismuth oxychlorides Bi18O22Cl8.5(BO3)0.5 and Bi18O22Cl8Se

Single crystals of two new quaternary bismuth oxychlorides, Bi18O22Cl8.5(BO3)0.5(1) and Bi18O22Cl8Se (2), have been serendipitously produced in syntheses starting from bismuth borate or oxyselenide and oxychloride. The crystal structure of 1 represents a high symmetry analog of the PbBi17O22Cl9 type structure, formed by double aliovalent (Pb2+ → Bi3+, 0.5Cl– → 0.5BO33−) substitution at the two respective cationic and anionic sites, while 2 is a full structural analog of PbBi17O22Cl9. Overall, their structures can be described as sequences of thick (16 Å) slabs (2D “host” structure) comprised of litharge–like layers and ribbons formed by edge-sharing oxocentered OBin, polyhedra (n = 4 and 5). The chloride anions fill the 7.6 Å channels with the triangular cross-section inside the slabs as well as the interlayer space wherein they are partially substituted by disordered BO33− groups or Se2− anions. Compound 1 is just the second example of a mixed halide–borate occupancy among bismuth compounds while 2 illustrates much broader perspectives of mixed oxyhalide–oxychalcogenide approach to construction of novel complex bismuth compounds. Both compounds make new contributions to the family of tunnel structures of anion-centered tetrahedra featuring wide trigonal channels filled by halide anions or more complex metal–halide “salt inclusions”.

Synthesis, biological evaluation, molecular docking, and MD simulation of novel 2,4-disubstituted quinazoline derivatives as selective butyrylcholinesterase inhibitors and antioxidant agents

Alzheimer’s disease is the most prevalent neurodegenerative disorder characterized by significant memory loss and cognitive impairments. Studies have shown that the expression level and activity of the butyrylcholinesterase enzyme increases significantly in the late stages of Alzheimer’s disease, so butyrylcholinesterase can be considered as a promising therapeutic target for potential Alzheimer’s treatments. In the present study, a novel series of 2,4-disubstituted quinazoline derivatives (6a–j) were synthesized and evaluated for their inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinestrase (BuChE) enzymes, as well as for their antioxidant activities. The biological evaluation revealed that compounds 6f, 6h, and 6j showed potent inhibitory activities against eqBuChE, with IC50 values of 0.52, 6.74, and 3.65 µM, respectively. These potent compounds showed high selectivity for eqBuChE over eelAChE. The kinetic study demonstrated a mixed-type inhibition pattern for both enzymes, which revealed that the potent compounds might be able to bind to both the catalytic active site and peripheral anionic site of eelAChE and eqBuChE. In addition, molecular docking studies and molecular dynamic simulations indicated that potent compounds have favorable interactions with the active sites of BuChE. The antioxidant screening showed that compounds 6b, 6c, and 6j displayed superior scavenging capabilities compared to the other compounds. The obtained results suggest that compounds 6f, 6h, and 6j are promising lead compounds for the further development of new potent and selective BuChE inhibitors.