Adaptation of the BaAl4 Type to Small Cations: The Case of NaGa4.

Single-phase NaGa4 samples were prepared by annealing stoichiometric element mixtures at 200 °C, 300 °C, and 450 °C in closed tantalum ampoules. No compositional homogeneity range was detected. While single crystals annealed at 200 °C feature a fully ordered crystal structure, a crystal annealed at 300 °C reveals a defect with mutual exchange of Na atoms and Ga2 dumbbells. The structure motif caused by the violation of translational symmetry resembles the CeMg2Si2 type of structure. The NaGa4 structure constitutes a branch of the BaAl4 type distinguished by a notably high c/a ratio (space group I4/mmm; a=4.2261(1) Å, c=11.2633(6) Å, c/a=2.67). This distortion enables the adaption of the BaAl4-type to small cations, when the further shortening of the apical-apical distance d(Ga-Ga) is not possible any more. Therefore, NaGa4 offers an adaption alternative to the monoclinic distortion observed in CaGa4 and YbGa4. Conductivity measurements validate the metallic behavior anticipated by NMR measurements in earlier studies.

A Quasi-Two-Dimensional Trilayered CsPbBr3 -based Dion-Jacobson Hybrid Perovskite toward High-Performance Photodetection.

Quasi-two-dimensional (Q-2D) Dion-Jacobson (DJ) organic-inorganic hybrid perovskites based on CsPbBr3 are promising candidates for photodetection. Previous studies have predicted that the photoresponse of such materials with high inorganic-layer numbers (n) will be more protruding in this portfolio. However, until now, only bilayered (n=2) CsPbBr3 -based DJ-type hybrid perovskites are obtained and the higher number of layers (n>2) remain completely unexplored, owing to the relatively high formation energies. Here, by incorporating diamine into the 3D CsPbBr3 motif, a new Q-2D trilayered CsPbBr3 -based DJ-type hybrid perovskite that contains organic cation and inorganic Cs metal, namely (4-AMP)Cs2 Pb3 Br10 (1, 4-AMP2+ =4-(aminomethyl)piperidinium, n=3), is obtained. Excitingly, 1 exhibits excellent photoresponse, superior to its single-layered and bilayered counterparts. The resulting photodetectors thus exhibit a large on/off ratio (>103 ), high photodetectivity (6.5×1010  Jones) and fast response speed (193 µs). As far as we know, 1 is the first Q-2D CsPbBr3 -based DJ-type hybrid perovskites with high n numbers. Our results may widen the range of the potential material in application of photodetection and will be helpful to design hybrid perovskites for other advanced optoelectronic devices.

Local magnetism in MnSiPt rules the chemical bond.

Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn-Mn bonds, deciding between competing crystal structures.

Assessing Cardiometabolic Health Risk Among U.S. Children Living in Grandparent-Headed Households.

PURPOSE: We evaluated children's cardiometabolic health (CMH) risk indicators and adverse childhood experiences (ACEs) stratified by family structure type (grandparent-headed, two-parent headed, and single-parent headed households). Separately, we assessed whether family structure type and number of ACEs were independently associated with the CMH risk indicators. DESIGN AND METHODS: Utilizing data from the 2017-2018 National Survey of Children's Health, we evaluated five CMH risk indicators (obesity, physical activity, secondhand smoke exposure, sleep, and sports participation). We used multivariable logistic regressions to assess the association of CMH risk indicators with family structure type and ACEs. We controlled for sex, age, race/ethnicity, health insurance, household poverty level, and overall health status. RESULTS: Among children aged 10-17 years (n = 24,885), we found the number of ACEs differed by family structure type (P < 0.001) and was independently associated with obesity, secondhand smoke exposure, sleep, and sports participation. Adjusting for all covariates except ACEs, family structure type was significantly associated with children's CMH risk; but after controlling for ACEs that association was attenuated - except for sleep (less adequate sleep in grandparent-headed households) and exposure to secondhand smoke (less exposure in single-parent headed households). CONCLUSIONS: ACEs were highest among children living in grandparent-headed households and independently associated with a majority of the CMH risk indicators. Findings suggest that children living in grandparent-headed households may be at elevated risk for poor CMH, potentially due to higher risk for ACEs. PRACTICE IMPLICATIONS: It is recommended to consider ACEs and family structure type when assessing CMH risk in children.

Prototype of Nitro Compound Vapor and Trace Detector Based on a Capacitive MIS Sensor.

A prototype of a nitro compound vapor and trace detector, which uses the pyrolysis method and a capacitive gas sensor based on the metal-insulator-semiconductor (MIS) structure type Pd-SiO2-Si, was developed and manufactured. It was experimentally established that the detection limit of trinitrotoluene trace for the detector prototype is 1 × 10-9 g, which corresponds to concentration from 10-11 g/cm3 to 10-12 g/cm3. The prototype had a response time of no more than 30 s. The possibility of further improving the characteristics of the prototype detector by reducing the overall dimensions and increasing the sensitivity of the MIS sensors is shown.

Chemical Bonding Analysis as a Guide for the Preparation of New Compounds: The Case of VIrGe and HfPtGe.

The chemical bonding of transition metal compounds with a MgAgAs-type of crystal structure is analyzed with quantum chemical position-space techniques. The observed trends in QTAIM Madelung energy and nearest neighbor electron sharing explain the occurrence of recently synthesized MgAgAs-type compounds, TiPtGe and TaIrGe, at the boundary to the TiNiSi-type crystal structure. These bonding indicators are used to identify favorable element combinations for new MgAgAs-type compounds. The new phases-the high-temperature VIrGe and the low-temperature HfPtGe-showing this type of crystal structure are prepared and characterized by powder X-ray diffraction and differential thermal analysis.

Crystal structure of the inter-metallic compound SrCdPt.

The crystal structure of the title compound, strontium cadmium platinum, adopts the TiNiSi structure type with the Sr atoms on the Ti, the Cd atoms on the Ni and the Pt atoms on the Si positions, respectively. The Pt atoms form cadmium-centred tetra-hedra that are condensed into a three-dimensional network with channels parallel to the b-axis direction in which the Sr atoms are located. The latter are bonded to each other in the form of six-membered rings with chair conformations. All atoms in the SrCdPt structure are situated on a mirror plane.

Zharchikhite, AlF(OH)2: a novel structure type related to α-PbO2.

The crystal structure of zharchikhite, AlF(OH)2, from the Zharchikhinskoe deposit (Buryatia, Russia) is solved here using single-crystal X-ray diffraction. The mineral is monoclinic, space group P21/c, a = 5.1788 (4), b = 7.8386 (4), c = 5.1624 (4) Å, ß = 116.276 (10)°, V = 187.91 (3) Å3 and Z = 4. Zharchikhite demonstrates a novel structure type roughly related to the α-PbO2 structure type and different from other compounds of the Al-F-OH system. The crystal structure of zharchikhite is based on the octahedral pseudoframework built from zigzag chains of edge-sharing AlF2(OH)4 octahedra; adjacent chains are linked via F vertices and the pseudoframework contains wide channels.

Flavonoidal alkaloids: Emerging targets for drug discovery from Nature's bounty.

This paper explores the potential of flavonoid alkaloids, a unique class of compounds that contain both flavonoid and alkaloid structures, as emerging targets for drug discovery. These compounds exhibit diverse biological activities, such as anti-inflammatory, anti-cancer, and anti-diabetic effects, which are attributed to the combination of different flavonoid scaffolds and alkaloid groups. Flavonoid alkaloids have attracted researchers' attention due to their diverse structures and important bio-activities. Therefore, this review summarizes recent advances in the extraction, purification, structural characterization, synthesis pathways and biological activities of flavonoid alkaloids from natural sources. Finally, the potential prospects and challenges associated with this class of compounds in pharmacological research are discussed along with details of a mechanistic investigation and future clinical applications in this research field.

The crystal structure of quaternary (Sn,Pb,Bi)Pt.

Quaternary (Sn,Pb,Bi)Pt was synthesized by melting of the elements in an evacuated silica glass ampoule. The crystal structure was established by single-crystal X-ray diffraction and adopts an atomic arrangement of the NiAs type with additional occupation of the voids. Decisive for the refinement was the composition of the crystals as determined by energy dispersive X-ray spectroscopy (EDXS), resulting in a formula of (Sn0.15Pb0.54Bi0.31)Pt.

Role of lone-pair electron localization in temperature-induced phase transitions in mimetite.

The crystal structure of mimetite Pb5(AsO4)3Cl, a phosphate with apatite structure-type has been investigated in situ at 123, 173, 273, 288, 353 and 393 K. A careful inspection of the diffraction pattern and subsequent structure refinements indicated that mimetite transforms from the monoclinic to the hexagonal polymorph with increasing temperature. At 123 K, a monoclinic superstructure, mimetite-2M, with cell parameters a = 20.4487 (9),  b = 7.4362 (2), c = 20.4513 (9) Å, ß = 119.953 (6)°, V = 2694.5 (2) Å3 and space group P21 was observed. From 173 to 353 K, the reflections of the supercell were evident only along one direction of the corresponding hexagonal apatite-cell and the structure transforms to the polymorph mimetite-M with space group P21/b and unit-cell parameters a = 10.2378 (3), b = 20.4573 (7), c = 7.4457 (2) Å, ß = 120.039 (5)°, V = 1349.96 (9) Å3. Only at higher temperature, i.e. 393 K, does mimetite adopt the hexagonal space group P63/m characteristic of apatite structure-types. The role of the electron lone pairs of Pb atoms in the phase transition was investigated through the analysis of the electron localization function (ELF) calculated based on the DFT-geometry optimized structures of the three polymorphs. The changes in spatial distribution of the 6s2 electron density during the phase transitions were explored by means of the Wannier Function Centres (WFCs) derived from ab initio molecular dynamics trajectories. In the high-temperature hexagonal structure the 6s2 electrons are spherically symmetric relative to the position of Pb atoms. At low temperature the maximum of 6s2 electron density is displaced relative to the position of Pb atom contributing to the polar interaction in the monoclinic polymorphs.

Superconductivity in non-centrosymmetric ZrNiAl and HfRhSn-type compounds.

We report the discovery of superconductivity in non-centrosymmetric compounds HfNiAl, ZrNiAl, ZrNiGa, and HfPtAl by measuring their electrical transport and thermodynamic properties. HfNiAl, ZrNiAl, and ZrNiGa crystallize in the ZrNiAl-type crystal structure, whereas HfPtAl crystallizes in the HfRhSn-type crystal structure. Superconducting transitions for HfNiAl, ZrNiAl, ZrNiGa, and HfPtAl are observed at 1.0 K, 1.0 K, 0.42 K, and 0.58 K, respectively. Using the Werthamer-Helfand-Hohenberg model, the zero-temperature upper critical fieldsµ0Hc2(0) were estimated to be 0.58 T, 0.24 T, 0.08 T, and 0.34 T for HfNiAl, ZrNiAl, ZrNiGa, and HfPtAl, respectively. The observed jump in electronic heat capacity (ΔCe/γT) across the superconducting transition is 1.3, 1.3, and 1.2 for HfNiAl, ZrNiAl, and HfPtAl, respectively. After the inclusion of the spin-orbit coupling in the band structure calculations, a total of six bands for ZrNiAl, HfPtAl, and ZrNiGa, and eight bands for HfNiAl were found to cross the Fermi level. Spin-orbit coupling induced maximum splitting (ΔEASOC/kBTc) of the electronic bands near the Fermi level was found to be 1697, 517, 1138, and 4230 for HfNiAl, ZrNiAl, ZrNiGa, and HfPtAl, respectively. Large variation of the antisymmetric spin-orbit coupling (ASOC) among these compounds provides a great opportunity to study the effects of ASOC on the superconducting pairing states.

[Advances in biosynthesis of cadinane sesquiterpenes].

Cadinanes are a class of bicyclic sesquiterpenes with complex stereochemistry and broad pharmacological activities, such as antibacterial, anti-inflammatory, and hypoglycemic activities. To date, structurally diverse and bioactive cadinane sesquiterpenes have been isolated and identified from a variety of plants and microorganisms. Moreover, deeper understandings on cadinane sesquiterpene synthases have been made. This article categorized the 124 new cadinanes which were published in the literatures in the past four years (2017-2020) into five structural types, and presented their pharmacological activities. We also illustrated the elucidation of the biosynthetic pathways for typical cadinanes, summarized the research progress on cadinane sesquiterpene synthases. Finally, current challenges and future prospects were proposed and discussed.

Synthesis, crystal structure and charge-distribution validation of a new alluaudite-type phosphate, Na2.22Mn0.87In1.68(PO4)3.

Na2.22Mn0.87In1.68(PO4)3, sodium manganese indium tris-(phosphate) (2.22/0.87/1.68), was obtained in the form of single crystals by a flux method and was structurally characterized by single-crystal X-ray diffraction. The compound belongs to the alluaudite structure type (space group C2/c) with general formula X(2)X(1)M(1)M(2)2(PO4)3. The X(2) and X(1) sites are partially occupied by sodium [occupancy 0.7676 (17) and 1/2] while the M(1) and M(2) sites are fully occupied within a mixed distribution of sodium/manganese(II) and manganese(II)/indium, respectively. The three-dimensional anionic framework is built up on the basis of M(2)2O10 dimers that share opposite edges with M(1)O6 octa-hedra, thus forming infinite chains extending parallel to [10]. The linkage between these chains is ensured by PO4 tetra-hedra through common vertices. The three-dimensional network thus constructed delimits two types of hexa-gonal channels, resulting from the catenation of M(2)2O10 dimers, M(1)O6 octa-hedra and PO4 tetra-hedra through edge- and corner-sharing. The channels are occupied by Na+ cations with coordination numbers of seven and eight.

Rietveld refinement of the langbeinite-type phosphate K2Ni0.5Hf1.5(PO4)3.

Polycrystalline potassium nickel(II) hafnium(IV) tris-(orthophosphate), a langbeinite-type phosphate, was synthesized by a solid-state method. The three-dimensional framework of the title compound is built up from two types of [MO6] octa-hedra [the M sites are occupied by Hf:Ni in ratios of 0.754 (8):0.246 (8) and 0.746 (8):0.254 (8), respectively] and [PO4] tetra-hedra are connected via O vertices. The K+ cations are located in two positions within large cavities of the framework, having coordination numbers of 9 and 12. The Hf, Ni and K sites lie on threefold rotation axes, while the P and O atoms are situated in general positions.

The crystal structure of KScP2O7.

Single crystals of KScP2O7, potassium scandium diphosphate, were grown in a borate flux. The title compound crystallizes isotypically with KAlP2O7 in space-group type P21/c, Z = 4. The main building block is an {ScP2O11}9- unit, forming layers parallel to (001). These layers are stacked along [001] via common corners of octa-hedral and tetra-hedral units to span up large hepta-gonal cavities that host the potassium cations with a coordination number of 10. The P-O-P bridging angle increases with increasing size of the octa-hedrally coordinated M III cation, as do the K-O distances within a series of KM IIIP2O7 compounds (M III = Al to Y with ionic radii r = 0.538 to 0.90 Å).

Redetermination of Sr2PdO3 from single-crystal X-ray data.

The crystal structure redetermination of Sr2PdO3 (distrontium palladium trioxide) was carried out using high-quality single-crystal X-ray data. The Sr2PdO3 structure has been described previously in at least three reports [Wasel-Nielen & Hoppe (1970 ▸). Z. Anorg. Allg. Chem. 375, 209-213; Muller & Roy (1971 ▸). Adv. Chem. Ser. 98, 28-38; Nagata et al. (2002 ▸). J. Alloys Compd. 346, 50-56], all based on powder X-ray diffraction data. The current structure refinement of Sr2PdO3, as compared to previous powder data refinements, leads to more precise cell parameters and fractional coordinates, together with anisotropic displacement parameters for all sites. The compound is confirmed to have the ortho-rhom-bic Sr2CuO3 structure type (space group Immm) as reported previously. The structure consists of infinite chains of corner-sharing PdO4 plaquettes inter-spersed by SrII atoms. A brief comparison of Sr2PdO3 with the related K2NiF4 structure type is given.

A new form of Cd3TeO6 revealing dimorphism.

Phase-formation studies in the system CdO-TeO3 using a CsCl/NaCl melt at comparatively low temperatures revealed that tricadmium orthotellurate(VI), Cd3TeO6, is dimorphic. The new modification of Cd3TeO6 is denoted as the ß-form and adopts the rhombohedral Mg3TeO6 structure type with one Cd and two O sites in general positions, and two Te sites with site symmetry each. In comparison with the previously reported monoclinic cryolite-type α-form that was prepared at higher temperatures, ß-Cd3TeO6 has a much lower density and most likely represents a metastable modification. Whereas the [TeO6] octa-hedra in both polymorphs are very similar and show only minor deviations from ideal values, the polyhedra around the CdII sites are different, with a distorted [CdO6] octa-hedron in both modifications but an additional [CdO8] polyhedron with a [4 + 4] coordination in the α-form.

Crystal structures of the triple perovskites Ba2K2Te2O9 and Ba2KNaTe2O9, and redetermination of the double perovskite Ba2CaTeO6.

Single crystals of Ba2K2Te2O9 (dibarium dipotassium nona-oxidoditellurate), (I), Ba2KNaTe2O9 (dibarium potassium sodium nona-oxidoditellurate), (II), and Ba2CaTeO6 (dibarium calcium hexa-oxidotellurate), (III), were obtained from KNO3/KI or KNO3/NaNO3 flux syntheses in platinum crucibles for (I) and (II), or porcelain crucibles for (III). (I) and (II) are isotypic and are members of triple perovskites with general formula A2[12co]A'[12co]B2[6o]B'[6o]O9. They crystallize in the 6H-BaTiO3 structure family in space-group type P63/mmc, with the A, A', B and B' sites being occupied by K, Ba, Te and a second Ba in (I), and in (II) by mixed-occupied (Ba/K), Ba, Te and Na sites, respectively. (III) adopts the A2[12co]B'[6o]B''[6o]O6 double perovskite structure in space-group type Fmm, with Ba, Ca and Te located on the A, B' and B'' sites, respectively. The current refinement of (III) is based on single-crystal X-ray data. It confirms the previous refinement from X-ray powder diffraction data [Fu et al. (2008). J. Solid State Chem.181, 2523-2529], but with higher precision.

Crystal structure of disilver(I) dizinc(II) iron(III) tris-(orthovanadate) with an alluaudite-type structure.

The title compound, Ag2Zn2Fe(VO4)3, has been synthesized by solid-state reactions and belongs to the alluaudite structure family. In the crystal structure, four sites are positioned at special positions. One silver site is located on an inversion centre (Wyckoff position 4b), and an additional silver site, as well as one zinc and one vanadium site, on twofold rotation axes (4e). One site on a general position is statistically occupied by FeIII and ZnII cations that are octa-hedrally surrounded by O atoms. The three-dimensional framework structure of the title vanadate results from [(Zn,Fe)2O10] units of edge-sharing [(Zn,Fe)O6] octa-hedra that alternate with [ZnO6] octa-hedra so as to form infinite chains parallel to [10]. These chains are linked through VO4 tetra-hedra by sharing vertices, giving rise to layers extending parallel to (010). Such layers are shared by common vanadate tetra-hedra. The resulting three-dimensional framework delimits two types of channels parallel to [001] in which the silver sites are located with four- and sixfold coordination by oxygen.