Single-crystal Synchrotron X-ray Diffraction Research Articles

Toward an understanding of the role of structural organization and point defects in the formation of functional pure and Tm3+-doped (Ca3-xSrx)(VO4)2 for diode-pumped and SRS lasers

Whitlockite-type polycrystalline and single-crystal (Ca3−xSrx)(VO4)2 solid solutions were successfully obtained by solid-state synthesis and Czochralski method, respectively. Synchrotron powder X-ray diffraction allowed to reveal actual compositions of polycrystalline (Ca3−xSrx)(VO4)2 solid solutions with х = 0.3, 0.54, 0.9, 1.2, 1.35 refined by Rietveld method, which are slightly different from the initial ones. Synchrotron X-ray single-crystal diffraction analysis of Czochralski-grown undoped (Ca1.8Sr1.2)(VO4)2 (CSVO) revealed its actual composition (Ca2.982(11)Sr0.031)(VО4)2. Difference between initial and refined compositions is analyzed and discussed. In the CSVO structure, Sr2+ ions partially occupy monocapped Ca2 and two-capped Ca3 trigonal prismatic sites and Ca2+ ions are in the Ca5 and Ca5A sites, forming two independent strongly distorted tetrahedral Ca5O4 and octahedral Ca5AO6 oxygen environments. Synchrotron X-ray single-crystal diffraction analysis together with X-ray absorption spectroscopic study of (Сa2.4Sr0.6)(VO4)2 doped with 0.5 and 1.0 wt% Tm2O3 (СSVO:0.5Tm and CSVO:1.0Tm) allowed to establish the absence of cations in the Ca5A site, the localization of Sr2+ ions in the Ca2 and Ca3 sites and additionally in octahedral Ca4 site together with Tm3+ ions, forming an individual eight-coordinated environment, in the refined compositions (Ca2.776(7)Sr0.210(4)Tm3+0.008(1))(VO4)2 and (Ca2.855(7)Sr0.140(7)Tm3+0.009(1)□0.022(7))(VO4)2, respectively, with vacancies (marked by a square,□) in the two-capped Ca1 trigonal prismatic site in the CSVO:1.0Tm structure. Additional interstitial oxygen, participating in the formation of the Tm3+ environment, found in the residual electron density, together with vacancies in the Ca1 site provides electroneutrality to CSVO:0.5Tm and CSVO:1.0Tm crystals. Several structural models of the coordination environment of Tm3+ ions were analyzed and the most correct one was proposed.

Diffusion dominant thermal transport in mixed valent Ba4Sn4Se9

New material developments are of paramount importance from the perspective of developing a fundamental understanding of material properties as well as transitioning from materials to devices. Among the different classes of materials of interest, mixed valence Sn compositions have been known to display technologically important properties and are of interest for the design and synthesis of novel compositions for targeted applications. Herein, we report on electronic, optical and thermal properties of the previously unexplored mixed valence composition Ba4Sn4Se9, a material with a direct optical band gap of 2.36 eV. As revealed by single crystal synchrotron X-ray diffraction, Ba4Sn4Se9 crystallizes in the orthorhombic space group Pnma with a large unit cell comprised of 58 atoms. Heat capacity data reveals a low Debye temperature with many low frequency optic modes. Our low temperature thermal conductivity data and analyses show that thermal diffusion dominates thermal transport above 80 K. Furthermore, high lattice anharmonicity contributes to the very low thermal conductivity. Our results and analyses will motivate further investigations of this as well as other compositions in the Ba-Sn-Se system, as well as other mixed valence chalcogenides for technological applications.

Electromechanical properties of uniaxial polar ionic plastic crystal [(C2H5)4N][FeBrCl3

Abstract Ferroelectric plastic crystals are an emerging class of materials that combine room temperature ferroelectricity and piezoelectricity with a high temperature plastic mesophase prior to melting. These materials offer possibilities for accessing different property parameter spaces from the state-of-the-art metal oxide and polymer ferroelectrics. Tetraethylammonium bromotrichloroferrite, [(C2H5)4N][FeBrCl3], has a unipolar wurtzite-like structure and thus may have potential for small but stable piezoelectric coefficients like the iso-symmetrical AlN. In this study, density functional theory was used to compute elastic compliance, piezoelectric coefficients, and dielectric constant values. Single crystals grown from aqueous solutions were evaluated via single crystal synchrotron x-ray diffraction, impedance spectroscopy and high and weak-field electromechanical characterization. Diffraction studies revealed that the anion tetrahedra orientated preferentially so that the Br− ion had a 30% alignment with the polarization vector. Electromechanical measurements found piezoelectric coefficients in the 5–9 pC N−1 and pm V−1 range. The piezoelectric coefficient (d 33) was most stable with 3.4% variation between 0.4 and 90 Hz and 0.5 and 3 V. Additional piezoelectric stability measurements were made as a function of DC bias field and temperature. Impedance measurements indicate contributions from either intrinsic effects unique to ionic plastic crystals, such as molecular rotation, or the extrinsic effect of electrode interfaces, both of which can play a role in the electromechanical response of the materials. The results show that [(C2H5)4N][FeBrCl3] has potential as a small signal piezoelectric that has a softer elastic moduli than AlN but a stiffer moduli than polyvinylidene fluoride, and thus occupies a unique parameter space.

Unexpected formation of FeIIFeIIIFeII- and FeIIFeIIFeII-trinuclear hexapyridineoximate helicates: synchrotron single-crystal X-ray structures

Template condensation of 2-acetylpyridineoxime with butyl ester of 1,3-propanediboronic acid in the presence of iron(II) affords a poorly separable mixture of complex products. Similar results were observed when Fe3+ ions were used for cross-linking in place of the diboronic acid. Prolonged crystallization of these mixtures gave crystals of perchlorate salts of a FeIIFeIIIFeII-trinuclear hexapyridineoximate cation and of an analogous FeIIFeIIFeII-intracomplex that crystallize with chloroform and dichloromethane solvent molecules, respectively. Both complexes were characterized by synchrotron single-crystal X-ray diffraction (XRD) experiments. The Fe–N distances of the two ‘terminal’ iron cations are virtually the same between these trinuclear complexes and unambiguously support assignments of oxidation number +2 and low-spin state (S = 0). The centers of the FeN6 -coordination polyhedra adopt geometries resembling trigonal antiprisms with distortion angles φ of approximately 40°. The FeO6 -coordination polyhedra possess an almost ideal Oh geometry with φ close to 60°. Each of these iron(II) or iron(III) µ3 -metallocenters acts as a bifunctional Lewis acid that cross-links two pseudoclathrochelate entities, formed by the ‘terminal’ iron(II) ions, to give an almost linear (the corresponding intramolecular Fe(2)…Fe(1)…Fe(3) angles are close to 180°) helical cation or intracomplex.

Diverse high-pressure chemistry in Y-NH3BH3 and Y-paraffin oil systems.

The yttrium-hydrogen system has gained attention because of near-ambient temperature superconductivity reports in yttrium hydrides at high pressures. We conducted a study using synchrotron single-crystal x-ray diffraction (SCXRD) at 87 to 171 GPa, resulting in the discovery of known (two YH3 phases) and five previously unknown yttrium hydrides. These were synthesized in diamond anvil cells by laser heating yttrium with hydrogen-rich precursors-ammonia borane or paraffin oil. The arrangements of yttrium atoms in the crystal structures of new phases were determined on the basis of SCXRD, and the hydrogen content estimations based on empirical relations and ab initio calculations revealed the following compounds: Y3H11, Y2H9, Y4H23, Y13H75, and Y4H25. The study also uncovered a carbide (YC2) and two yttrium allotropes. Complex phase diversity, variable hydrogen content in yttrium hydrides, and their metallic nature, as revealed by ab initio calculations, underline the challenges in identifying superconducting phases and understanding electronic transitions in high-pressure synthesized materials.

Dehydration kinetics of nanoconfined water in beryl probed by high temperature single crystal synchrotron X-ray diffraction

Understanding changes in material properties through external stimuli plays a key role in validating the expected performance of materials and engineering material properties in a controlled manner. Here, we introduce a fundamental protocol to deduce dehydration reactions kinetics of water confined in nanopore channels, with the cyclosilicate beryl as the scaffold of interest, using time-resolved synchrotron X-ray diffraction (SXRD), in the temperature interval of 298–1038 K. The temperature-dependent intensity (I)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(I)$$\\end{document} of the strongest reflection (112) was used as the crystallite variable. An estimation of an isobaric thermal crystallite coefficient, k\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k$$\\end{document}, analogous with the isobaric thermal expansion coefficient, established the rate of relative crystallization as a function of temperature, ∂I∂T\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{\\partial I}{\\partial T}$$\\end{document}. A plot of lnk\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$lnk$$\\end{document} and 1T\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{1}{T}$$\\end{document} gives rise to two kinetic steps, indicating a slow dehydration stage up to ~ 700 K and a fast dehydration stage up to the investigated temperature 1038 K. The crystal structure of beryl determined up to 1038 K, in temperature increment as small as 10 K, indicates the presence of channel ions Na and Fe and a gradual decrease of water upon heating.

Stabilization of N6 and N8 anionic units and 2D polynitrogen layers in high-pressure scandium polynitrides

Nitrogen catenation under high pressure leads to the formation of polynitrogen compounds with potentially unique properties. The exploration of the entire spectrum of poly- and oligo-nitrogen moieties is still in its earliest stages. Here, we report on four novel scandium nitrides, Sc2N6, Sc2N8, ScN5, and Sc4N3, synthesized by direct reaction between yttrium and nitrogen at 78-125 GPa and 2500 K in laser-heated diamond anvil cells. High-pressure synchrotron single-crystal X-ray diffraction reveals that in the crystal structures of the nitrogen-rich Sc2N6, Sc2N8, and ScN5 phases nitrogen is catenated forming previously unknown N66− and N86− units and ∞2(N53−)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\!\\,}_{\\infty }{\\!\\,}^{2}({{{{{\\rm{N}}}}}}_{5}^{3-})$$\\end{document} anionic corrugated 2D-polynitrogen layers consisting of fused N12 rings. Density functional theory calculations, confirming the dynamical stability of the synthesized compounds, show that Sc2N6 and Sc2N8 possess an anion-driven metallicity, while ScN5 is an indirect semiconductor. Sc2N6, Sc2N8, and ScN5 solids are promising high-energy-density materials with calculated volumetric energy density, detonation velocity, and detonation pressure higher than those of TNT.

Negative Linear Compressibility and Interlayer Gap Closure in Layered Rare-Earth Hydroxyhalide (YCl(OH)2) under High Pressure.

Layered materials have attracted extensive attention due to their exceptional physical and chemical properties. Understanding the structural evolution of such materials under high pressure is crucial for the development of new functional materials. In this study, the structure evolution of the synthesized layered rare-earth hydroxyhalide YCl(OH)2 under high pressures up to approximately 9.4 GPa was explored by using a diamond anvil cell combined with synchrotron single-crystal X-ray diffraction. Simultaneously, high-pressure Raman spectroscopy experiment was conducted to 10.3 GPa. Our findings indicate that YCl(OH)2 maintains its symmetry within the experimental pressure range. The pressure-volume data of YCl(OH)2 were fitted to the third-order Birch-Murnaghan equation of state (EoS) to derive its EoS parameters including zero-pressure unit-cell volume (VT0), isothermal bulk modulus (KT0), and its pressure derivative (K'T0): VT0 = 142.47 (1) Å3, KT0 = 38.2 (18) GPa, and K'T0 = 9.8 (1). However, the unit-cell parameters a, b, and c exhibit a distinct compressional behavior, with the a-axis being the most compressible and the b-axis being the least. Particularly noteworthy is the observation that YCl(OH)2 displays a negative linear compressibility along the b-axis within the pressure range of 0.4-5.3 GPa. Further detailed structure refinement and Raman spectroscopy analyses indicate that the anomalous behavior of the b-axis could be attributed to the formation of the O-H···O hydrogen bonding chains along the b direction. Moreover, the coordination number of Y3+ increased from 8 to 9 as the pressure reached 5.3 GPa due to the reduction of the interlayer spacing upon compression, ultimately leading to the closure of the interlayer gap.

High-pressure and high-temperature synthesis of crystalline Sb3 N5.

A chemical reaction between Sb and N2 was induced under high-pressure (32-35 GPa) and high-temperature (1600-2200 K) conditions, generated by a laser heated diamond anvil cell. The reaction product was identified by single crystal synchrotron X-ray diffraction at 35 GPa and room temperature as crystalline antimony nitride with Sb3 N5 stoichiometry and structure belonging to orthorhombic space group Cmc21 . Only Sb-N bonds are present in the covalent bonding framework, with two types of Sb atoms respectively forming SbN6 distorted octahedra and trigonal prisms and three types of N atoms forming NSb4 distorted tetrahedra and NSb3 trigonal pyramids. Taking into account two longer Sb-N distances, the SbN6 trigonal prisms can be depicted as SbN8 square antiprisms and the NSb3 trigonal pyramids as NSb4 distorted tetrahedra. The Sb3 N5 structure can be described as an ordered stacking in the bc plane of bi- layers of SbN6 octahedra alternated to monolayers of SbN6 trigonal prisms (SbN8 square antiprisms). The discovery of Sb3 N5 finally represents the long sought-after experimental evidence for Sb to form a crystalline nitride, providing new insights about fundamental aspects of pnictogens chemistry and opening new perspectives for the high-pressure chemistry of pnictogen nitrides and the synthesis of an entire class of new materials.

Structure and titanium distribution of feiite characterized using synchrotron single-crystal X-ray diffraction techniques

Abstract A solid solution of the mineral feiite (Fe3TiO5) was recently discovered in a shock-induced melt pocket of the Shergotty martian shergottite. It is particularly interesting for its potential as an indicator of pressure-temperature (P-T) and oxygen fugacity in martian crustal and mantle material. To date, complete crystallographic analysis of feiite has not been conducted, as the mineral was previously analyzed by electron backscatter diffraction on micrometer-size grains (Ma et al. 2021). Here we report a convergent crystal-structure model for feiite based on synchrotron single-crystal X-ray diffraction data collected on three grains of feiite synthesized at 12 GPa and 1200 °C. Feiite adopts the CaFe3O5 structure type (Cmcm, Z = 4), which is composed of two octahedral M1 and M2 sites and one trigonal prismatic M3 site (M = metal) in a ratio of 1:2:1. The three feiite grains with composition Ti0.46–0.60Fe3.54–3.40O5 were best modeled by substituting Ti4+ into only the octahedral M2 site, accounting for 30% of this site. Comparisons of the measured average bond lengths in the coordination polyhedra with the optimized Ti4+–O, Fe2+–O, and Fe3+–O bond lengths suggest that ferrous iron occupies the trigonal M3 site, while iron is mixed valence in the octahedral M1 and M2 sites. The Ti4+ and Fe3+ content constrained by our crystal-chemical analyses suggests that at least ~30% of the available iron must be ferric (i.e., Fe3+/Fetotal = 0.3) for the sample synthesized at 12 GPa and 1200 °C and higher P-T conditions may be needed to form the end-member feiite (Fe32+TiO5).

High-pressure synthesis of acentric sodium pyrocarbonate, Na2[C2O5

The inorganic pyrocarbonate salt Na2[C2O5] crystallizes in the acentric, monoclinic space group P21 with Z = 2. It contains monovalent alkali metal cations together with isolated pyrocarbonate anions. The [C2O5]2--groups consist of two planar [CO3]2--groups which are slightly tilted with respect to each other around the bridging oxygen atom. Na2[C2O5] was synthesized in a laser-heated diamond anvil cell at 20(2) GPa by heating a mixture of Na2[CO3] + CO2 to ≈800(200) K. Its crystal structure was obtained by single crystal synchrotron X-ray diffraction and confirmed by density functional theory-based calculations in combination with Raman spectroscopy. Second harmonic generation measurements verified the acentric space group symmetry. The crystal structure is characterized by alternating layers of Na+-cations and [C2O5]2--complex anions.

Synthesis of Ultra-Incompressible and Recoverable Carbon Nitrides Featuring CN4 Tetrahedra.

Carbon nitrides featuring three-dimensional frameworks of CN4 tetrahedra are one of the great aspirations of materials science, expected to have a hardness greater than or comparable to diamond. After more than three decades of efforts to synthesize them, no unambiguous evidence of their existence has been delivered. Here, the high-pressure high-temperature synthesis of three carbon-nitrogen compounds, tI14-C3 N4 , hP126-C3 N4 , and tI24-CN2 , in laser-heated diamond anvil cells, is reported. Their structures are solved and refined using synchrotron single-crystal X-ray diffraction. Physical properties investigations show that these strongly covalently bonded materials, ultra-incompressible and superhard, also possess high energy density, piezoelectric, and photoluminescence properties. The novel carbon nitrides are unique among high-pressure materials, as being produced above 100GPa they are recoverable in air at ambient conditions.

Structural and vibrational properties of cage-type Sc5Ru6Sn18 superconductor under pressure using synchrotron X-ray diffraction and Raman spectroscopy

We report detailed structural investigations of cage-type quasi-skutterudite compound Sc5Ru6Sn18 using synchrotron single-crystal and powder x-ray diffraction. Single-crystal x-ray diffraction studies at ambient temperature revealed that the Sc5Ru6Sn18 compound has a tetragonal symmetry in the I41/acd space group setting with a = 13.58Å and c = 27.14Å, similar to other R5Rh6Sn18 (R = Y, Sc, Lu) cage-type compounds. The electrical resistivity ρ(T) revealed the presence of a sharp superconducting (SC) transition at Tc = 4.07K. The ρ(T) of Sc5Ru6Sn18 above Tc shows a smooth decrease with decreasing temperature without any evident anomalies. Systematic temperature dependent synchrotron x-ray powder diffraction (XRPD) studies covering 400 to 110K shows that the Sc5Ru6Sn18 system remain in the tetragonal I41/acd structure in this temperature range without any anomalous behaviour in the unit-cell parameters. High-pressure (HP) synchrotron XRPD revealed a smooth reduction in the unit-cell parameters up to ~7GPa which can be well described by a third-order Birch-Murnaghan equation providing the bulk modulus of the system to be ~102.6GPa. This system is found to several Raman modes below 300cm-1. We could follow the pressure evolution of four Raman modes, all of which show a smooth hardening with pressure up to ~7GPa. Our results call for systematic HP studies of the SC properties of the title system.

Effect of chromium substitution on structural and optical properties of Ca3(VO4)2 for laser and SRS applications

Crystal structures of Czochralski-grown Ca3(VO4)2 single crystals doped with over-stoichiometric 0.01, 0.05, and 0.1 wt% Cr2O3 (CVO:Cr) are solved and refined. A whitlockite-like structure with five Ca sites, two-capped (Ca1 and Ca3) and mono-capped (Ca2) trigonal prisms, distorted octahedron (Ca4) and tetrahedron (Ca5), is determined for CVO:Cr. Single-crystal synchrotron X-ray diffraction analysis revealed the presence of chromium in Ca2, Ca3, Ca4 sites. In CVO:Cr, chromium has octahedral (Cr3+) and tetrahedral (Cr4+) coordination, which suggests structural superpositions of CaO8, CaO7, CaO6 and Cr3+O6 or Cr4+O4 polyhedra. X-ray diffraction, EPR and spectroscopic studies showed that green or yellow color of CVO:Cr is related to chromium valence state, Cr3+ or Cr4+, respectively. An increase in the Cr4+ concentration is accompanied by increased vacancy content in two of three vanadium sites. Structural behavior of transition metal ions with a variable formal charge (Co, Mn, Cr) in CVO structure is summarized, analyzed and discussed. Three absorption bands around 23900, 16300 and 14000 cm−1, typical for Cr3+ ions, are revealed in the UV-VIS spectra of green samples. An additional broad band with a maximum at 21254 cm−1 refers to Cr4+ ions, the appearance of which after annealing in air was established by X-ray diffraction analysis.

High-pressure adsorption phenomena in natural and synthetic zeolites with EAB topology

The high-pressure behaviour and the crystal-fluid interaction of zeolites with EAB topology were investigated by in-situ single-crystal and powder synchrotron X-ray diffraction, both on synthetic and natural samples. The experiments were conducted using a diamond anvil cell and different pressure transmitting fluids, including: the non-penetrating silicone oil and the potentially penetrating methanol:ethanol:H2O = 16:3:1 mixture, methanol and distilled H2O. The zeolites intrinsic compressional behaviour investigated with a non-penetrating fluid showed the significant role of the extra framework population on the bulk compressibility. Notably, within the first ∼0.5 GPa of the silicone oil ramp, the bulk modulus (KV0 = βV0−1) resulted to be KV0 = 62(1) GPa for the natural bellbergite and KV0 = 16(4) GPa for the synthetic K-analogue. The synthetic EAB zeolites demonstrated a high host capacity for methanol molecules, which were not able to penetrate the natural bellbergite cavities. A comparative analysis between the behaviour of zeolites with EAB topology and structurally similar zeolites, such as erionite (ERI topology) and offretite (OFF), is provided.

Stabilization Of The CN35- Anion In Recoverable High-pressure Ln3O2(CN3) (Ln = La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates.

A series of isostructural Ln3O2(CN3) (Ln = La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure(25-54 GPa) high-temperature (2000-3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD)as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln3O2(CN3) solids are composed of the hitherto unknown CN35- guanidinate anion - deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln3O2(CN3) (Ln = La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln3O2(CN3) compounds are recoverable to ambient conditions. The stabilization of the CN35- guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry.

Stabilization Of The CN35− Anion In Recoverable High‐pressure Ln3O2(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) Oxoguanidinates

AbstractA series of isostructural Ln3O2(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high‐pressure (25–54 GPa) high‐temperature (2000–3000 K) conditions in laser‐heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single‐crystal X‐ray diffraction (SCXRD) as well as corroborated by X‐ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln3O2(CN3) solids are composed of the hitherto unknown CN35− guanidinate anion—deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln3O2(CN3) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln3O2(CN3) compounds are recoverable to ambient conditions. The stabilization of the CN35− guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry.

Stabilization of Guanidinate Anions [CN3]5- in Calcite-Type SbCN3.

The stabilization of nitrogen-rich phases presents a significant chemical challenge due to the inherent stability of the dinitrogen molecule. This stabilization can be achieved by utilizing strong covalent bonds in complex anions with carbon, such as cyanide CN- and NCN2-carbodiimide, while more nitrogen-rich carbonitrides are hitherto unknown. Following a rational chemical design approach, we synthesized antimony guanidinate SbCN3 at pressures of 32-38 GPa using various synthetic routes in laser-heated diamond anvil cells. SbCN3, which is isostructural to calcite CaCO3, can be recovered under ambient conditions. Its structure contains the previously elusive guanidinate anion [CN3]5-, marking a fundamental milestone in nitridocarbonatechemistry. The crystal structure of SbCN3 was solved and refined from synchrotron single-crystal X-ray diffraction data and was fully corroborated by theoretical calculations, which also predict that SbCN3 has a direct band gap with the value 2.20 eV. This study opens a straightforward route to the entire new family of inorganic nitridocarbonates.

High-pressure reactions between the pnictogens: the rediscovery of BiN.

We explore chemical reactions within pnictogens with an example of bismuth and nitrogen under extreme conditions. Understanding chemical reactions between Bi and N, elements representing the first and the last stable elements of the nitrogen group, and the physical properties of their compounds under ambient and high pressure is far from being complete. Here, we report the high-pressure high-temperature synthesis of orthorhombic Pbcn BiN (S.G. #60) from Bi and N2 precursors at pressures above 40GPa. Using synchrotron single-crystal X-ray diffraction on the polycrystalline sample, we solved and refined the compound's structure and studied its behavior and compressibility on decompression to ambient pressure. We confirm the stability of Pbcn BiN to pressures as low as 12.5(4)GPa. Below that pressure value, a group-subgroup phase transformation occurs, resulting in the formation of a non-centrosymmetric BiN solid with a space group Pca21 (S.G. #29). We use ab initio calculations to characterize the polymorphs of BiN. They also provide support and explanation for our experimental observations, in particular those corresponding to peculiar Bi-N bond evolution under pressure, resulting in a change in the coordination numbers of Bi and N as a function of pressure within the explored stability field of Pbcn BiN.

Zinc(II) and nickel(II) complexes with N-[2-(2-diethylphoshponylethyliminomethyl)phenyl]-4-methylbenzenesulfonamide: Synthesis, structure, and photoluminescence properties

Two Zn(II) and Ni(II) complexes derived from the N-[2-(2-diethylphosphonylethyliminomethyl)phenyl]-4-methylbenzenesulfonamide ligand (HL) with stoichiometry ML2 (M = Zn, Ni) have been synthesized. Their structures have been established using elemental analysis, IR, 1H NMR, UV–Vis spectroscopy, and synchrotron single-crystal X-ray diffraction. The Zn(II) and Ni(II) metal sites therein adopt the tetrahedral configuration. The DMSO and toluene solutions of the Zn(II) complex manifest photoluminescence in the blue-violet spectral range characterized by PL maxima at 436 and 432 nm and quantum yields of 0.15 and 0.30, respectively.