Arsenic-Containing Chalcophosphate Molecular Anions

Hydrothermal synthesis and structural characterization of a novel cadmium-organic framework

Helium droplets provide the possibility to study phenomena at the very low temperatures at which quantum mechanical effects are more pronounced and fewer quantum states have significant occupation probabilities. Understanding the migration of either positive or negative charges in liquid helium is essential to comprehend charge-induced processes in molecular systems embedded in helium droplets. Here, we report the resonant formation of excited metastable atomic and molecular helium anions in superfluid helium droplets upon electron impact. Although the molecular anion is heliophobic and migrates toward the surface of the helium droplet, the excited metastable atomic helium anion is bound within the helium droplet and exhibits high mobility. The atomic anion is shown to be responsible for the formation of molecular dopant anions upon charge transfer and thus, we clarify the nature of the previously unidentified fast exotic negative charge carrier found in bulk liquid helium.

A mononuclear cobalt(II) salophen-type complex: Synthesis, theoretical and experimental electronic absorption and infrared spectra, crystal structure, and predicting of second- and third-order nonlinear optical properties.

Synthesis, biological investigation, calf thymus DNA binding and docking studies of the sulfonyl hydrazides and their derivatives

A new polymorph of anhydrous sodium alendronate, C4H12NO7P2Na, has been synthesized and characterized by single crystal X-ray diffraction as well as infrared spectroscopy and thermal analysis. The title compound crystallizes in the monoclinic P21/c space group. Asymmetric unit consists of one alendronic anion and one sodium cation. An interplay of classical strong O-H…O, N-H…O and non-classical weak C-H…O hydrogen bonds creates 3D framework in the crystal. Contrary to previously reported sodium alendronate salts, in which Na+ cation is surrounded by six-coordinated sphere, in compound (1), the Na+ cation is five-coordinated in a distorted trigonal-bipyramidal geometry. In order to provide a detailed investigation of the molecular arrangement in view of intermolecular interactions, the title compound was compared with alendronic acid and other known alkali metal alendronate salts, retrieved from the Cambridge Crystal Structure Database. The intercontacts were qualitatively and quantitatively compared using Hirshfeld surface analysis. It highlights that strong O…H/H…O and subtle H…H contacts play an influential role in the total surface area. The Me+…H/H…Me+ and Me+…O/O…Me+ contacts are meaningful as well. These evidently simple systems show a diverse complexity. Moreover, the powder X-ray diffraction, DSC, thermogravimetry/derivative thermogravimetry, and FT-IR results are also reported.

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Structural and vibrational analysis of copper(II) 1,3-benzothiazol-2-yl[imino(phenyl)methyl]azanide

AlPO4-5 is a zeolite (structure type: AFI) with 6-and 12-membered rings, and 12-membered ring channels have a relatively large pore size of 7.3 and can take in a variety of molecules (Fig. 1).Although there have been many studies on the adsorption properties of AlPO4-5 as a molecular sieve, surprisingly, its crystal structure remains unclear.For example, the most accepted space group of AlPO4-5 is P6cc with unit cell parameters of a ~ 13.7 and c ~ 8.5 (e.g., [1]), but several space groups with lower symmetry have also been proposed (e.g., [2,3]).Furthermore, although the existence of satellite reflections suggesting the existence of modulated structures has recently been reported under high pressure [4], a detailed analysis of these satellite reflections has not been performed due to the weakness of the observed satellite reflections.Here we revisit to perform x-ray diffraction using a relatively large single crystal of AlPO4-5.Single crystal x-ray diffraction experiments for calcined AlPO4-5 single crystals were conducted using a laboratory-based x-ray diffractometer (Rigaku/Synergy custom) with a Mo rotating anode (Rigaku/MicroMax-007), a confocal x-ray mirror (Rigaku/VariMax-MoHF), and a hybrid pixel semiconductor detector (Rigaku/Hypix-6000HE).The diffraction images were obtained for single crystals of about 100 m in diameter, and we first found the satellite peaks of q = 0.3725(3) c* up to 2 nd order even at ambient conditions.The observed q value is similar to the previously reported value under high pressure [4], and its noninteger value indicates that the AlPO4-5 has an incommensurate structure.We also tested the thermal stability of the incommensurate structure by single crystal x-ray diffraction and Raman spectroscopy using a purpose-built high-temperature chamber under vacuum.The detailed analysis of the incommensurate structure and its thermal stability is going to be discussed.Figure 1.Crystal structure of AlPO4-5 along c-axis (left) and a 12-membered channel (right).

Anhydrous Sr(CF3COO)2 and Ba(CF3COO)2 open-framework structures featuring three-dimensional connectivity of metal-oxygen polyhedra were crystallized from a mixture of water and CF3COOH. Crystallization was induced via evaporation of the solvent mixture under a dry nitrogen flow. This approach differs from that routinely employed for crystallization of metal trifluoroacetates, which achieves solvent evaporation by heating under air and yields hydrated salts. Thermogravimetric and differential thermal analysis as well as single-crystal and synchrotron powder X-ray diffraction were employed to characterize the alkaline-earth trifluoroacetate products. Neither thermal analysis nor single-crystal X-ray diffraction detected the presence of crystallization water molecules, demonstrating these trifluoroacetates can be obtained in anhydrous form. Single-crystal X-ray diffraction studies showed that Sr(CF3COO)2 and Ba(CF3COO)2 are isostructural and crystallize in the rhombohedral R3̅ space group. Both compounds belong to the class of organic-inorganic extended hybrids and exhibit an open-framework structural motif with three-dimensional connectivity of the metal-oxygen polyhedra and one-dimensional channels along the c axis. The channels are decorated with the trifluoromethyl groups of the trifluoroacetate ligands, and their average (minimum) diameters are ∼3.75 (2.60) and 3.45 (2.25) Å for Sr(CF3COO)2 and Ba(CF3COO)2, respectively. This size range is comparable to the kinetic diameter of small molecules such as hydrogen (2.3 Å). Chemical substitution of barium for strontium affects not only the diameter of the channels but also the spatial arrangement of the trifluoromethyl groups within the channels and the coordination environment of the metal atoms. The different coordination requirements of the strontium and barium atoms are accommodated through the displacement of one of the two chemically distinct trifluoroacetate ligands relative to the metal center.

Study of the distribution of the molecular orientation in thick polyethylene samples by X-ray diffraction, infra-red dichroism and Raman spectroscopy

A new one-dimensional organic-inorganic hybrid antimony halide, (C10H13N4)[SbI4]·H2O, was synthesized via a hydrothermal method and structurally characterized by single-crystal X-ray diffraction. The crystal structure comprises infinite [SbI4]- chains separated by protonated organic cations and lattice water molecules, forming a supramolecular architecture stabilized by hydrogen bonding and other noncovalent interactions. Phase purity was confirmed by powder X-ray diffraction. At the same time, Hirshfeld surface and intermolecular energy analyses reveal that electrostatic interactions and hydrogen bonding play a dominant role in the crystal packing. Vibrational properties investigated by FT-IR and Raman spectroscopy, supported by density functional theory calculations, confirm the structural integrity of both the organic and inorganic components. Optical studies show visible photoluminescence under UV excitation, and the optical band gap is estimated to be about 3.06 eV, while theoretical calculations predict a band gap close to 2.9 eV, indicating semiconducting behavior. Thermal analysis further demonstrates a well-defined multistep decomposition process consistent with the structural composition. These results highlight the structural stability and optoelectronic potential of this new antimony-based hybrid material.

Two anhydrous polymorphs of the novel antiviral medicine nirmatrelvir were discovered during the development of Paxlovid, Pfizer's oral Covid-19 treatment. A comprehensive experimental and computational approach was necessary to distinguish the two closely related polymorphs, herein identified as Forms 1 and 4. This approach paired experimental methods, including powder X-ray diffraction and single-crystal X-ray diffraction, solid-state experimental methods, thermal analysis, solid-state nuclear magnetic resonance and Raman spectroscopy with computational investigations comprising crystal structure prediction, Gibbs free energy calculations, and molecular dynamics simulations of the polymorphic transition. Forms 1 and 4 were ultimately determined to be enantiotropically related polymorphs with Form 1 being the stable form above the transition temperature of ∼17 °C and designated as the nominated form for drug development. The work described in this paper shows the importance of using highly specialized orthogonal approaches to elucidate the subtle differences in structure and properties of similar solid-state forms. This synergistic approach allowed for unprecedented speed in bringing Paxlovid to patients in record time amidst the pandemic.

The influence of the transition metal (Ti, V, Zr, W) doping on the carbon matrix nanostructuring during the thin film growth and subsequent annealing is investigated. Pure and metal-doped amorphous carbon films (a-C, a-C:Me) were deposited at room temperature by nonreactive magnetron sputtering. The carbon structure of as-deposited and postannealed (up to 1300 K) samples was analyzed by x-ray diffraction (XRD) and Raman spectroscopy. The existence of graphenelike regions in a-C is concluded from a (10) diffraction peak. A comparison of the XRD and Raman results suggests that XRD probes only the small amount of 2–3 nm large graphenelike regions, whereas the majority of the sp2 phase is present in smaller distorted aromatic clusters which are probed only by Raman spectroscopy. Annealing leads to an increase in the graphene size and the aromatic cluster size. During the carbon film growth the addition of metals enhances ordering of sp2 carbon in sixfold aromatic clusters compared to a-C; Ti, and Zr showing the strongest effect, W the lowest. This order qualitatively corresponds with the catalytic activity of the respective carbides found during graphitization of carbide-doped graphites published in the literature. With annealing, carbide crystallite formation and growth occurs in a-C:Me films, which destroys the initial carbon structure, reduces the size of the initially formed aromatic clusters and the differences in carbon structure introduced by different dopants. For high annealing temperatures the carbon structure of a-C:Me films is similar to that of a-C, and is determined only by the annealing temperature.

9,10-diphenylanthracene (DPA) single crystal is a promising scintillator material for fast-neutron detection. Two centimetre-sized polymorph crystals of DPA were grown by melting and solution methods (DPA-Melt and DPA-Solution, respectively), and characterised by single-crystal X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, fluorescence spectroscopy, UV-Vis absorbance spectroscopy, and thermogravimetric/differential scanning calorimetry. The DPA-Melt crystal possessed a P21/n structure, with excitation bands at approximately 331, 348, 367, and 387 nm, and the strongest emission wavelength at approximately 454 nm. On the other hand, the DPA-Solution crystal possessed a C2/c structure, with excitation bands at approximately 335, 353, 372, and 396 nm, and the strongest emission wavelength at approximately 468 nm. The two kinds of DPA crystals have the same molecular formula but different crystal structures, crystal lattice constants, and cell parameters. The theoretical density of the DPA-Solution crystal was 1.239 g/cm3, while that of the DPA-Melt crystal was 1.211 g/cm3. The two types of crystals exhibited the same melting point, but the thermal stability of the DPA-Solution crystal is better than that of the DPA-Melt crystal.

Catalytic reactions of coke with dioxygen and steam over alkaline-earth-metal-doped cerium-zirconium mixed oxides