Search Results (2,321)

In order to design antimicrobial species, a series of methacrylate (Macr) complexes, [Cu(HBzIm)₂(Macr)₂] (1), [Cu₂(HBzIm)₂(Macr)₄] (2), [Cu(2-MeBzIm)₂(Macr)₂] (3), [Cu₂(2-MeBzIm)₂(Macr)₄] (4), and [Cu(5,6-Me₂BzIm)₂(Macr)₂] (5) (HBzIm = benzimidazole, 2-MeBzIm = 2-methylbenzimidazole, and 5,6-Me₂BzIm = 5,6-dimethylbenzimidazole) were synthesized and characterized by several spectral techniques, as well as by single crystal X-ray diffraction. The mononuclear species exhibit a distorted octahedral stereochemistry, while the binuclear types, with a paddle-wheel structure, adopt a square pyramidal surrounding. The methacrylate acts either as a chelate or a bridge, while all benzimidazole derivatives are coordinated as unidentate. The supramolecular networks are developed by both intermolecular π–π stacking interactions and hydrogen bonds. The antimicrobial assays provided both complexes the ability to inhibit planktonic strain proliferation, as well as to adhere on inert substratum. All complexes exhibit a moderate antimicrobial activity, both in regards to standard and clinical isolate strains, the most active being compound 5 against Candida albicans, with a minimum inhibitory concentration (MIC) of 0.156 mg/mL. It is worth mentioning that complex 1 inhibited the microbial adhesion of the clinical Escherichia coli strain and complex 2 constrained that of the clinical C. albicans strain. Full article

The interaction of preorganized iron(II) pivalate complexes with aromatic N-donor ligand (pyridine (py) or 2,2′-bipyridine (bpy)) and 1,4-diaminobutane (dab, putrescine) in anhydrous acetonitrile yielded a new 2D coordination polymer [Fe(piv)₂(dab)₂]_n (1, piv = Me₃CCO₂^–). The molecular structure of 1 in crystal was determined by single-crystal X-ray diffraction analysis and ATR-FTIR spectroscopy. Full article

The crystal chemistry of syngenite K₂Ca(SO₄)₂·H₂O and its lattice dynamics under low and high temperatures and high pressure were studied. The research facilities used include in situ temperature variable single-crystal (SCXRD) and powder X-ray diffraction (PXRD), in situ PXRD under high pressure (HP), thermal analysis (DSC and TGA), and Raman spectroscopy. For the first time, a detailed study of syngenite in the range of negative temperatures down to −180 °C was performed. It indicates the absence of phase transitions in the range from −180 °C to 240 °C. The largest expansion of the structure is observed along the α₁₁, which is consistent with the layered architecture. The minor thermal expansion along the α₂₂ is observed in the plane of the [Ca(SO₄)₂]²⁻ layer, formed by the bassanite-type chains. The study of powder samples at HP up to 20 GPa was carried out using synchrotron radiation and a diamond anvil cell. The phase transition is registered at 10 GPa. After the decompression, the syngenite post-phase becomes partially amorphized. Full article

Callicarpa giraldii Hesse ex Rehd. is an endemic plant in China and has long been used as a traditional medicine in several provinces. Although the plant has been reported to contain flavonoids, triterpenes, and alkaloids, this study represents the first report of the isolation of phyllocladane-type diterpenoids, a relatively rare class of compounds. In this study, 18 new phyllocladane-type diterpenoids (7–24) were isolated and structurally elucidated, including eight uncommon 3,4-seco phyllocladane-type diterpenoids (15–22) and two unusual phyllocladane-type diterpene dimers (23–24), along with six known analogues (1–6). Their structures were elucidated by a comprehensive analysis of 1D and 2D NMR, IR, and HRESIMS data. The absolute configurations were determined by single crystal X-ray diffraction experiments, DFT NMR calculations, and TDDFT ECD calculations. Based on the obtained and reported spectroscopic data, we refined a rule to distinguish phyllocladane-type diterpenoids from their diastereomeric ent-kaurane-type compounds. Additionally, the isolated compounds were evaluated for their in vitro anti-neuroinflammatory activity against lipopolysaccharide (LPS)-induced inflammation in BV-2 microglial cells. Compounds 5, 10, 13, 18, 19, and 20 showed moderate inhibitory activity at the concentration of 20 μM, with compounds 5 and 13 markedly reducing the mRNA levels of the pro-inflammatory cytokines IL-1β, IL-6, and TNF-α at this concentration. Full article

The anisotropic magnetoresistance (AMR) effect is widely used in microscale and nanoscale magnetic sensors. In this study, we investigate the correlation between AMR and the crystal structure, epitaxial relationship, and magnetic properties of Co₅₀Fe₅₀ thin films deposited on rigid MgO and flexible mica substrates. The AMR ratio is approximately 1.6% for CoFe films on mica, lower than the 2.5% observed in epitaxially grown films on MgO substrates. The difference is likely due to the well-defined easy axis in the single domain epitaxial thin films on MgO, which enhances the AMR ratio. Microscopic strain induced by lattice mismatch and bending on flexible substrates were determined using grazing incidence X-ray diffraction and extended X-ray absorption fine structure techniques. These results showed that neither microscopic nor macroscopic strain (below 0.5%) affects the AMR ratio on mica, suggesting its suitability for magnetic sensors in flexible and wearable devices. Additionally, investigating M-H loops under various growth temperatures, lattice mismatch conditions, and bending strains could further benefit the fabrication and integration of the micro-scale magnetic sensors in the microelectronic industry. Full article

Tegoprazan is a potassium ion-competitive acid blocker (P-CAB) and a novel inhibitor of gastric acid secretion. The compound exists in two crystalline polymorphs, A and B, whose structures had not previously been reported. In this study, both polymorphs were analyzed by liquid- and solid-state NMR, revealing identical tautomeric states. Using this information, the crystal structures were determined from laboratory powder X-ray diffraction data by simulated annealing and Rietveld refinement. Both forms were found to crystallize in the monoclinic space group P2₁, with Z = 4 and two independent molecules in the asymmetric unit (Z′ = 2). To assess the stability and reliability of the refined structures, we attempted geometry optimization and vibrational analysis using DFT-D methods. However, due to the high conformational complexity of Z′ = 2 systems, these calculations failed to converge or produced imaginary frequencies. Instead, single-point energy calculations were performed on the refined models. The resulting relative energy differences, together with solubility data, van’t Hoff enthalpies, and DSC profiles, consistently indicated that Polymorph A is more stable than Polymorph B. These results highlight the challenges of structure validation via DFT-D for complex molecular crystals and demonstrate the value of integrating experimental and computational approaches for polymorph characterization. Full article

Several CNN pincer Pd(II) complexes including chiral complexes 1a–e with 2-phenyl-6-(oxazolinyl)pyridines and achiral ones 2a–c with N-substituted-2-aminomethyl-6-phenylpyridines were prepared. In addition, the preparation of the achiral PCN pincer Pd(II) complexes 3a–e with aryl-based phosphinite–imine ligands and chiral 4a–c with aryl-based phosphinite–imidazoline ligands was also performed. Among them, the PCN Pd(II) pincers 3a–e were new complexes and were readily synthesized from commercially available materials in only two steps. The new complexes were characterized through elemental analyses, namely ¹H NMR, ¹³C{¹H} NMR, and ³¹P{¹H} NMR spectroscopies. Furthermore, the molecular structure of complex 3a was determined via X-ray single-crystal diffraction analysis. In the presence of EtAlCl₂, Et₂AlCl, or methylaluminoxane (MAO), the CNN pincer Pd(II) complexes and PCN pincer Pd(II) complexes exhibited excellent activities and monomer conversion rates in norbornene addition polymerization. Surprisingly, the CNN pincer Pd(II) complexes exhibited a higher conversion rate (99.5%) with Et₂AlCl as the cocatalyst, while the PCN pincer Pd(II) complexes showed a higher conversion rate (98.8%) with MAO. Full article

Coordination polymers containing zinc and imidazolium-based dicarboxylate ligands, [L^R]⁻, were synthesized by reacting zinc acetate with HL^R compounds, 1. The resulting complexes were characterized and structurally identified using single-crystal X-ray diffraction, revealing polymeric structures for the complexes [Zn(L^R)₂]_n (R = Gly, 2a; βAla, 2b) and [Zn(L^Leu)₂(H₂O)₂]_n (2c). In these structures, the [L^R]⁻ ligands adopt a bridging monodentate μ-κ¹-O¹,κ¹-O³ coordination mode, resulting in distorted tetrahedral (2a, 2b) or octahedral (2c) geometries around the zinc center. When the synthesis was carried out in the presence of amino acids, mixed ligand complexes [Zn(L^R)(aa)(H₂O)]_n (R = aa = Val, 2d, and R = aa = Ile, 2e) were formed. Complexes 2d–2e were also structurally characterized using single-crystal X-ray crystallography, revealing that the ligand [L^R]⁻ maintained the same coordination mode, while the zinc center adopted a five-coordinated geometry. The cytotoxic activity of complexes 2a–2e was evaluated against three cancer cell lines and one non-cancerous cell line. Remarkably, these complexes exhibited higher toxicity against cancer cells than against the non-cancerous cell line, and they showed greater selectivity than carboplatin, a commonly used chemotherapy drug. Although, in general, these complexes did not surpass the selectivity of gemcitabine, complex 2c stood out for exhibiting a selectivity index value similar to that of gemcitabine against melanoma cells. Among the series, compounds 2a–2c demonstrated the highest activity, with 2a being the only complex with some selective activity against lung cancer. Complex 2b was the most active, though with low selectivity, while complex 2c exhibited the highest selectivity for melanoma and bladder cancer (selectivity index of 3.0). Full article

Sixteen polyketides, including six new compounds (1–2, and 5–8), were isolated from the culture of the marine sponge-associated fungus Neopestalotiopsis sp. SCSIO 41422. Their structures were elucidated through NMR, MS spectroscopic analyses, calculated electronic circular dichroism, quantum chemical NMR calculations, and X-ray single-crystal diffraction. To screen and evaluate the inhibitory activity of these polyketides in renal fibrosis, a TGF-β1-stimulated HK-2 cell model was used. All tested compounds (1, 5–8, and 11–12) at 10 µM showed obvious anti-fibrotic activity by inhibiting TGF-β1-induced α-SMA expression and extracellular matrix production (collagen I and fibronectin). Among them, gamahorin A (1) was shown to be the most potent and the most promising inhibitor against renal fibrosis. Full article

The third-generation semiconductor single-crystal silicon carbide (SiC), as a typical difficult-to-machine material, improves the chemical reaction rate on the SiC surface during the polishing process, which is key to realizing efficient chemical mechanical polishing (CMP). In this paper, a new core-shell structure Fe₃O₄@MIL-100(Fe) magnetic catalyst was successfully synthesized, which can effectively improve the reaction rate during the SiC polishing procesSs. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), and was used as a heterogeneous photocatalyst for chemical mechanical polishing, and the polishing results of SiC were optimized using response surface methodology (RSM). The experimental results show that the surface roughness of SiC can reach the minimum value of 0.78 nm when the polishing pressure is 0.06 MPa, the polishing speed is 60 rpm, and the polishing flow rate is 12 mL/min. The results of the study provide theoretical support for the visible photocatalysis-assisted CMP of SiC. Full article

A series of novel NNN pincer manganese complexes based on pyrazole skeleton 4 were efficiently synthesized in a two-step process. All of the new complexes were fully characterized by ¹H, ¹³C NMR spectra. Furthermore, the molecular structures of complexes 4a and 4c were also determined by X-ray single-crystal diffraction. The manganese(I) catalysts obtained showed efficient catalytic activity in the α-alkylation reaction of ketones with alcohols. Under optimal reaction conditions, the expected products were procured with moderate to high yields. Full article

Structural rearrangements in metal–organic supramolecules constructed from the coordination of Cu(II) with m-xpt (m-xylylenebis(pyridyltriazole)) are investigated upon their interaction with 1,4-diazabicyclo[2.2.2]octane (dabco) and carbon dioxide-enriched air. The binuclear [Cu₂(m-xpt)₂]⁴⁺ complexes react with dabco to produce a carbonate-bridged trinuclear complex, [Cu₃(m-xpt)₃(µ-CO₃)]⁴⁺, and an oxalate-bridged binuclear complex, [Cu₂(m-xpt)₂(µ-C₂O₄)]²⁺, where carbonate and oxalate likely originate from CO₂ and dabco, respectively. The trinuclear complex reassembles the original dimer upon the removal of the carbonate ion. Similarly, polymeric [Cu(o-xpt)(PF₆)]_n, formed from Cu(I) and o-xpt (o-xylylenebis(pyridyltriazole)) coordination, undergoes oxidation in CO₂-enriched air to yield a tetranuclear Cu(II) complex, Cu₄(o-xpt)₃(μ₄-CO₃)(μ₂-OH)(μ₂-OCOCH₃)⁴⁺. The reaction progress is monitored by UV-Vis spectroscopy, and the major products are characterized by single-crystal X-ray diffraction. Full article

Thermoelectric technology, which converts heat and electricity into each other, has been attracting attention from the perspective of efficient energy utilization. Recently, eco-friendly and cost-effective Cu-based thermoelectric materials have been actively studied. In particular, efforts have been made to improve thermoelectric properties and enhance performance through the formation of solid solutions. This study examines the formation and thermoelectric properties of Cu-chalcogenide solid solutions between eskebornite (tetragonal CuFeSe₂) and chalcopyrite (tetragonal CuFeS₂), synthesized as CuFeSe_2−yS_y (y = 0–2) using solid-state synthesis. These compounds share similar crystal structures, which enable the formation of solid solutions that enhance phonon scattering and may potentially improve thermoelectric performance. As the S content (y) increased, the lattice parameters a and c decreased, attributed to the smaller ionic radius of S²⁻ compared to Se²⁻, as X-ray diffraction analysis identified single-phase regions for 0 ≤ y ≤ 0.4 and 1.6 ≤ y ≤ 2, respectively. However, for 0.8 ≤ y ≤ 1.2, a composite phase of eskebornite and chalcopyrite formed, indicating incomplete solid solution behavior in the intermediate range. Thermoelectric measurements showed a sharp increase in electrical conductivity with increasing S content, alongside a transition in the Seebeck coefficient from positive (p-type) to negative (n-type), attributed to the intrinsic semiconducting nature of the end-member compounds. Eskebornite behaves as a p-type semiconductor, whereas chalcopyrite is n-type, and their combination affects the carrier type and concentration. Despite these changes, the power factor did not show significant improvement due to the inverse relationship between electrical conductivity and the Seebeck coefficient. The thermal conductivity decreased significantly with solid solution formation, with CuFeSe_0.4S_1.6 exhibiting the lowest value of 0.97 Wm⁻¹K⁻¹ at 623 K, a result of enhanced phonon scattering at lattice imperfections and the mass fluctuation effect. This value is lower than the thermal conductivity values of single-phase eskebornite or chalcopyrite. However, the reduction in thermal conductivity was insufficient to compensate for the modest power factor, resulting in no substantial enhancement in the thermoelectric figure of merit. Full article

Five new coordination compounds that included three coordination polymers and two supramolecular complexes were obtained by reactions of different cadmium salts (tetrafluoroborate, nitrate, and perchlorate) with dianiline chromophores, 4,4′-diaminodiphenylmethane (ddpm), and 4,4′-diaminodiphenylethane (ddpe). The crystal structures were studied by single-crystal X-ray analysis. The coordination arrays with the ddpm chromophore included {[Cd(OH)(H₂O)(ddpm)₂](BF₄)}_n (1) as a one-dimensional (1D) coordination garland chain, {[Cd(NO₃)(ddpm)₂](H₂O)(NO₃)}_n (2) as a two-dimensional (2D) coordination layer, and [Cd(bpy)₂(ddpm)₂](ddpm)(NO₃)₂ (3) as a supramolecular complex. The products with the ddpe chromophore were identified as {[Cd(phen)₂(ddpe)](ClO₄)₂}_n (4) in the form of a linear coordination chain and [Cd(phen)₃](ClO₄)₂(ddpe)_0.5(CH₃CN)_0.5 (5) as a supramolecular complex. The extension of coordination arrays in 1, 2, and 4 was achieved via dianiline ligands as bidentate linkers and additionally via bridging of nitrate anions in 2. The diversification of products became possible due to usage of 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) as co-ligands forming the terminal corner fragments [Cd(bpy)₂]²⁺, [Cd(phen)₂]²⁺, and [Cd(phen)₃]²⁺ in 3–5, respectively. The assembling of coordination entities occurred via the interplay of hydrogen bonds with the participation of amino groups, water molecules, and inorganic anions. Two dianilines were powerful luminophores in the crystalline phase, while the photoluminescence in 1–5 was considerably weaker than in the pure ddpm and ddpe luminophores and redistributed along the spectrum. Full article

In this study, single crystals of previously reported Schiff base copper (II) (Cu) and nickel (II) (Ni) complexes were synthesized; a structural analysis was performed using data measured at high temperatures, 298 K and 410 K; and CIF and electron density maps were obtained. The purpose of this study was to examine the accuracy of high-temperature measurements in X-ray crystal structure analyses and the details of atomic movement. Various data (statistics such as standard deviation) obtained from the structural analysis, such as the lattice constants, temperature factors, and electron density in cases without phase transitions, were compared. In addition, the anisotropic temperature factors were statistically processed. In the electron density map, the electron density tended to decrease at high temperatures. Looking at the two-dimensional fingerprint plot constructed from the Hirshfeld surface analysis, the intermolecular interactions between chlorine atoms and hydrogen atoms in the Cu changed significantly with the temperature change. In addition, the change in the anisotropic temperature factor of chlorine was significant. Moreover, a difference was observed in the analytical data at room temperature and high temperatures, which is thought to be useful for creating a model of temperature dependence. Full article