Multilayer Diffraction Reveals That Colloidal Superlattices Approach the Structural Perfection of Single Crystals
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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Understanding the Instability of the Halide Perovskite CsPbI 3 through Temperature-Dependent Structural Analysis
Despite the tremendous interest in halide perovskite solar cells, the structural reasons that cause the all-inorganic perovskite CsPbI 3 to be unstable at room temperature remain mysterious, especially since many tolerance-factor-based approaches predict CsPbI 3 should be stable as a perovskite. Here single-crystal X-ray diffraction and X-ray pair distribution function (PDF) measurements characterize bulk perovskite CsPbI3 from 100 to 295 K to elucidate its thermodynamic instability. While Cs occupies a single site from 100 to 150 K, it splits between two sites from 175 to 295 K with the second site having a lower effective coordination number, which, along with other structural parameters, suggests that Cs rattles in its coordination polyhedron. PDF measurements reveal that on the length scale of the unit cell, the Pb-I octahedra concurrently become greatly distorted, with one of the I-Pb-I angles approaching 82° compared to the ideal 90°. The rattling of Cs, low number of Cs-I contacts, and high degree of octahedral distortion cause the instability of perovskite-phase CsPbI 3 . These results reveal the limitations of tolerance factors in predicting perovskite stability and provide detailed structural information that suggests methods to engineer stable CsPbI 3 -based solar cells.
36 MATERIALS SCIENCE↗
Deviation from Debye-Waller behavior in single crystalline freestanding Ni O membranes studied via ultrafast electron diffraction
Here, we realize single-crystal freestanding NiO films on SiN membranes, enabling thin-film scattering experiments with little or no substrate background signal. These membrane samples provide a critical platform for performing ultrafast electron diffraction (UED) to probe the response of the lattice to laser excitation. We show that epitaxial NiO films on a water-soluble Sr 2 CaAl 2 O 6 buffer layer on SrTiO 3 substrates can be transferred as freestanding films to the SiN membranes while maintaining the epitaxial character of the films. An above-gap photoexcitation (𝜆 =266 nm) incident on the sample stimulates an initial lattice response of the order of 1.1 ps, followed by the persistence of this state for more than 20 ps. We observe typical Debye-Waller behavior in peaks with 𝑞 above the (220) family, but a distinct deviation from this behavior is seen in low-𝑞 peaks. We relate this behavior to a dynamic decrease in sample mosaicity in response to the optical pump of the order of 3% that endures for approximately 4 ps. We suspect that this dynamic mosaicity is due to laser-induced strain propagation. This work demonstrates the viability of the thin-film transfer method for UED and paves the way for the study of the dynamic response of antiferromagnetic thin-film oxides.
Wisser, Jacob J. [Stanford Univ., CA (United State↗
Psilocybin: crystal structure solutions enable phase analysis of prior art and recently patented examples
Psilocybin {systematic name: 3-[2-(dimethylamino)ethyl]-1 H -indol-4-yl dihydrogen phosphate} is a zwitterionic tryptamine natural product found in numerous species of fungi known for their psychoactive properties. Following its structural elucidation and chemical synthesis in 1959, purified synthetic psilocybin has been evaluated in clinical trials and has shown promise in the treatment of various mental health disorders. In a recent process-scale crystallization investigation, three crystalline forms of psilocybin were repeatedly observed: Hydrate A, Polymorph A, and Polymorph B. The crystal structure for Hydrate A was solved previously by single-crystal X-ray diffraction. This article presents new crystal structure solutions for the two anhydrates, Polymorphs A and B, based on Rietveld refinement using laboratory and synchrotron X-ray diffraction data, and density functional theory (DFT) calculations. Utilizing the three solved structures, an investigation was conducted via Rietveld method (RM) based quantitative phase analysis (QPA) to estimate the contribution of the three different forms in powder X-ray diffraction (PXRD) patterns provided by different sources of bulk psilocybin produced between 1963 and 2021. Over the last 57 years, each of these samples quantitatively reflect one or more of the hydrate and anhydrate polymorphs. In addition to quantitatively evaluating the composition of each sample, this article evaluates correlations between the crystal forms present, corresponding process methods, sample age, and storage conditions. Furthermore, revision is recommended on characterizations in recently granted patents that include descriptions of crystalline psilocybin inappropriately reported as a single-phase `isostructural variant.' Rietveld refinement demonstrated that the claimed material was composed of approximately 81% Polymorph A and 19% Polymorph B, both of which have been identified in historical samples. In this article, we show conclusively that all published data can be explained in terms of three well-defined forms of psilocybin and that no additional forms are needed to explain the diffraction patterns.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
β-Octabromo- and β-Octakis(trifluoromethyl)isocorroles: New Sterically Constrained Macrocyclic Ligands
Here, we present a study of the acid-induced demetalation of two sterically hindered copper corroles, Cu β-octabromo-meso-triphenylcorrole (Cu[Br 8 TPC]) and β-octakis(trifluoromethyl)-meso-tris(p-methoxyphenyl)corrole (Cu[(CF 3 ) 8 TpOMePC]). Unlike reductive demetalation, which affords the free-base β-octabromocorrole, demetalation of Cu[Br 8 TPC] under non- reductive conditions (CHCl 3 /H 2 SO 4 ) resulted in moderate yields of free-base 5- and 10-hydroxy isocorroles. The isomeric free bases could be complexed to Co II and Ni II , affording stable complexes. Only reductive demetalation was found to work for Cu[(CF 3 ) 8 TpOMePC], affording a highly saddled, hydrated corrole, H 3 [5-OH,10-H-(CF 3 ) 8 TpOMePC], where the elements of water had added across C5 and C10. Interaction of this novel free base with Co II resulted in Co[iso-10-H-[CF 3 ) 8 TpOMePC], a Co II 10-hydro isocorrole. Finally, the new metal complexes were all characterized by single-crystal X-ray diffraction analysis and, despite their sterically hindered nature, were found to exhibit almost perfectly planar isocorrole cores.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Er{sub 1.33}Pt{sub 3}Ga{sub 8}: A modulated variant of the Er{sub 4}Pt{sub 9}Al{sub 24}-structure type
Single crystals of Er{sub 1.33}Pt{sub 3}Ga{sub 8} were synthesized in a molten Ga flux. Er{sub 1.33}Pt{sub 3}Ga{sub 8} can be considered to be a modulated variant of the Er{sub 4}Pt{sub 9}Al{sub 24}-structure type, where the partial occupancies are ordered. Indeed, the presence of weak satellite reflections indicates a complex organization and distribution of the Er and Ga atoms within the [ErGa] slabs. The structure has been solved based on single crystal X-ray diffraction data in the monoclinic superspace group X2/m(0β0)00 with a commensurate modulated vector q=1/3b*. Precession images also indicate diffusion in the perpendicular direction indicating a partial disorder of this arrangement from layer to layer. In addition, Er{sub 1.33}Pt{sub 3}Ga{sub 8} shows antiferromagnetic ordering at T{sub N}~5 K. - Graphical abstract: A precession image of the hk0 zone showing weak, periodic, unindexed reflections indicating modulation and representation of the commensurate [ErGa] layer showing the waving modulated occupation. - Highlights: • Single crystals of Er{sub 1.33}Pt{sub 3}Ga{sub 8} were grown from gallium flux. • The structure of Er{sub 1.33}Pt{sub 3}Ga{sub 8} is compared to Er{sub 4}Pt{sub 9}Al{sub 24}. • Structure has been solved in the monoclinic superspace group X2/m(0β0)00 with a commensurate modulated vector q=1/3b*.
36 MATERIALS SCIENCE↗
Metal–Organic Framework Supported Single Site Chromium(III) Catalyst for Ethylene Oligomerization at Low Pressure and Temperature
A chemically and thermally stable, mesoporous, crystalline metal–organic framework, NU-1000, serves as a structurally well-defined support for catalytic reactions. Depositing chromium(III), a metal widely used in homogeneous ethylene oligomerization catalysts, onto the Zr6 node of NU-1000 allows for the atomically precise determination of the structure of the Cr3+ catalyst through single-crystal X-ray diffraction studies. Chromium modification of NU-1000 was accomplished via solvothermal deposition in MOFs (SIM); termed Cr-SIM-NU-1000, the elaborated material features individual Cr atoms directed in single-site fashion into the mesopore of NU-1000. It was found that NU-1000 serves to stabilize the catalyst against both the typical chemical deactivation of homogeneous systems and leaching from heterogeneous systems. Cr-SIM-NU-1000 exhibits superior catalytic activity, as compared to Cr2O3, for ethylene oligomerization, with 20% conversion at a turnover frequency of about 60 h–1 and products ranging from C8–C28. Given that this catalysis occurs at low temperature (ambient) and low pressure (1 bar C2H4), along with minimal quantity of cocatalyst, the high activity shown by Cr-SIM-NU-1000 enables significant reduction in materials usage and waste. Postcatalytic characterization reveals Cr-SIM-NU-1000 remains intact with no leaching under the reaction conditions.
catalysis (heterogeneous), materials and chemistry↗
Hydrothermal synthesis, structure, heterogeneous catalytic activity and photoluminescent properties of a novel homoleptic Sm(III)-organic framework
A novel metal-organic framework, (H{sub 2}pip){sub n}[Sm{sub 2}(pydc){sub 4}(H{sub 2}O){sub 2}]{sub n} (1) (H{sub 2}pydc=2,6-pyridinedicarboxylic acid, H{sub 2}pip=piperazine) has been synthesized under hydrothermal conditions and characterized by the elemental analysis, inductively coupled plasma (ICP) spectrometer, fourier transform infrared (FT-IR) spectra, thermogravimetric analysis (TGA), single crystal X-ray diffraction analysis and powder X-ray diffraction (PXRD). The structure of 1 was determined to be three-dimensional, linked along Sm-O-Sm chains. The asymmetric unit consisted of one singly anionic fragment consisting of Sm(III) coordinated to two H{sub 2}pydc ligands and one water, and one half of a protonated H{sub 2}pip, which sits on an inversion center. 1 exhibited luminescence emission bands at 534 nm at room temperature when excited at 440 nm. Its thermal behavior and catalytic performance were investigated and the selectivity was measured as 100% for the oxidation of thymol to thymoquinone. - Graphical abstract: A novel 3D lanthanide-organic framework has been synthesized under hydrothermal conditions. The thermal behavior and catalytic performance of 1 were investigated and its selectivity was measured as 100% for the oxidation of thymol to thymoquinone.
36 MATERIALS SCIENCE↗
Solvent exchange in a metal–organic framework single crystal monitored by dynamic in situ X-ray diffraction
Understanding the processes by which porous solid-state materials adsorb and release guest molecules would represent a significant step towards developing rational design principles for functional porous materials. To elucidate the process of liquid exchange in these materials, dynamic in situ X-ray diffraction techniques have been developed which utilize liquid-phase chemical stimuli. Using these time-resolved diffraction techniques, the ethanol solvation process in a flexible metal–organic framework [Co(AIP)(bpy) 0.5 (H 2 O)]·2H 2 O was examined. The measurements provide important insight into the nature of the chemical transformation in this system including the presence of a previously unreported neat ethanol solvate structure.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Synthesis of Lanthanide-Based Intermetallic Silicides
Lanthanide-containing materials are of interest because of their useful magnetic and electronic behavior. To study this intrinsic behavior, researchers need high-quality single crystals to avoid interference from grain boundaries or defects commonly found in polycrystalline samples. One method for growing single crystals is metal-flux synthesis, an approach that promotes crystal growth at lower reaction temperatures thus providing access to complex intermetallic phases. My project focuses on synthesizing novel lanthanide-containing intermetallic silicides related to previously reported f-element compounds with the Gd1??Fe4Si10?? structure type. I investigated reactions targeting lanthanum, praseodymium, neodymium, samarium, europium, and gadolinium-containing products, and used scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) to identify promising lanthanide-containing phases. I prepared reactions by loading lanthanide oxides, Co, Si, Al, and Ga into alumina crucibles in a 0.2:1:1:10:10 Ln2O3/Co/Si/Al/Ga mmol ratio, where Ln = La, Nd, Pr, Sm, Eu, or Gd. The reactions were sealed in quartz tubes, heated in a furnace, and centrifuged to separate crystals from excess flux. Afterwards, I mechanically isolated single crystals and prepared them for characterization. Pr-, Nd-, and Sm-containing reactions were confirmed through SEM-EDS to have formed the targeted quaternary phase. Single crystal X-ray diffraction (SC-XRD) data showed the Nd-containing crystals exhibited a hexagonal unit cell associated with the Gd1??Fe4Si10?? structure type. La- and Eu-containing reactions instead formed competing Co(Al/Ga/Si)3 phase crystals. Single-crystal XRD, powder XRD, and magnetic susceptibility and heat-capacity measurements will be collected for the remaining lanthanide-containing crystals. This data will help determine the complete crystal structure of the lanthanide analogues, their phase purity and whether they exhibit localized magnetic behavior, magnetic ordering, or other electronic signatures that can be compared with the previously reported actinide analogues. The disordered structure of this intermetallic family is associated with unusual magnetic and electronic behavior meaning lanthanide analogues may show potential as thermoelectric materials. Developing new thermoelectric candidate materials is relevant to energy efficiency and waste-heat recovery, which supports DOE’s broader goal of advancing science and technology solutions for America’s energy needs.
37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
Magnetism of single crystalline breathing pyrochlore spinel AgInCr 4 S 8
Single crystals of AgInCr 4 S 8 are grown by chemical vapor transport and crystallographic ordering of Ag/In that results in a breathing pyrochlore motif of Cr 3+ is verified by x-ray and neutron diffraction. Long-range antiferromagnetic order is observed below a Néel temperature of 𝑇 N ≈ 9.6 K. The magnetic properties are characterized using ac and dc magnetization, specific heat capacity, and single crystal neutron diffraction measurements. The specific heat data are characterized by a small lambda anomaly near 9.5 K and the estimated magnetic entropy reaches ≈ $\frac{1}{3}$ of the expected value by 3𝑇 N , suggesting significant short-range order in the paramagnetic phase. Single crystal neutron diffraction evidences an incommensurate spin structure with propagation vector 𝒌 = (0,0,𝛿) and 𝛿 = 0.343 at 5 K. The minimal model that accounts for the data consists of ferromagnetic layers of Cr atoms, with magnetic moments lying in the plane of the layers and modulating in the perpendicular direction to form a helical structure propagating along 𝒌. Furthermore, this study represents a rare investigation of single crystals within the family of breathing pyrochlore materials.
Frustrated magnetism↗
Luminescent Properties of DOBDC Containing MOFs: The Role of Free Hydroxyls
A novel metal–organic framework (MOF), Mn-DOBDC, has been synthesized in an effort to investigate the role of both the metal center and presence of free linker hydroxyls on the luminescent properties of DOBDC (2,5-dihydroxyterephthalic acid) containing MOFs. Co-MOF-74, RE-DOBDC (RE–Eu and Tb), and Mn-DOBDC have been synthesized and analyzed by powder X-ray diffraction (PXRD) and the fluorescent properties probed by UV–Vis spectroscopy and density functional theory (DFT). Mn-DOBDC has been synthesized by a new method involving a concurrent facile reflux synthesis and slow crystallization, resulting in yellow single crystals in monoclinic space group C2/c. Mn-DOBDC was further analyzed by single-crystal X-ray diffraction (SCXRD), scanning electron microscopy–energy-dispersive spectroscopy (SEM-EDS), and photoluminescent emission. Results indicate that the luminescent properties of the DOBDC linker are transferred to the three-dimensional structures of both the RE-DOBDC and Mn-DOBDC, which contain free hydroxyls on the linker. In Co-MOF-74 however, luminescence is quenched in the solid state due to binding of the phenolic hydroxyls within the MOF structure. Finally, Mn-DOBDC exhibits a ligand-based tunable emission that can be controlled in solution by the use of different solvents.
36 MATERIALS SCIENCE↗
Synthesis, disorder and Ising anisotropy in a new spin liquid candidate PrMgAl 11 O 19
Here we report the successful synthesis of large single crystals of triangular frustrated PrMgAl 11 O 19 using the optical floating zone technique. Single crystal x-ray diffraction (XRD) measurements unveiled the presence of quenched disorder within the mirror plane, specifically ~7% of Pr ions deviating from the ideal 2d site towards the 6h site. Magnetic susceptibility measurements revealed an Ising anisotropy with the c-axis being the easy axis. Despite a large spin–spin interaction that develops below ~10 K and considerable site disorder, the spins do not order or freeze down to at least 50 mK. The availability of large single crystals offers a distinct opportunity to investigate the exotic magnetic state on a triangular lattice with an easy axis out of the plane.
36 MATERIALS SCIENCE↗
Efficient extraction of inorganic selenium from water by a Zr metal–organic framework: investigation of volumetric uptake capacity and binding motifs
Strict monitoring and control of selenium concentrations in freshwater supplies is critical to safeguarding human health and aquatic life. A handful of previously investigated sorbents exhibit noteworthy gravimetric (mg g -1 ) Se uptake capacities; however, often display insufficient volumetric (mg cm -3 ) capacities, thereby requiring large volumes of material for commercial implementation. In this paper, in pursuit of mitigating this material inefficiency, we investigated the selenite (SeO 3 2- ) and selenate (SeO 4 2- ) affinity of MOF-808, a Zr-based metal–organic framework with a high density of potential Se oxyanion binding sites. MOF-808 recorded exceptional volumetric and gravimetric Se oxyanion capacities of 133 mg g -1 (127 mg cm -3 ) and 118 mg g -1 (112 mg cm -3 ) for aqueous selenite and selenate, respectively. Single-crystal X-ray diffraction studies revealed that selenite and selenate can bind at the MOF node via two distinct binding motifs, an η 2 μ 2 motif in which the oxyanion coordinates to two different metal atoms in a single node, and a μ 2 motif in which the oxyanion interacts with only a single metal atom. Finally and furthermore, powder X-ray diffraction (PXRD) patterns and N 2 adsorption/desorption isotherms confirm the retention of bulk crystallinity and porosity after the uptake of Se oxyanions.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Graphite resistive heated diamond anvil cell for simultaneous high-pressure and high-temperature diffraction experiments
High-pressure and high-temperature experiments using a resistively heated diamond anvil cell have the advantage of heating samples homogeneously with precise temperature control. Here, we present the design and performance of a graphite resistive heated diamond anvil cell (GRHDAC) setup for powder and single-crystal x-ray diffraction experiments developed at the Extreme Conditions Beamline (P02.2) at PETRA III, Hamburg, Germany. In the GRHDAC, temperatures up to 2000 K can be generated at high pressures by placing it in a water-cooled vacuum chamber. Temperature estimates from thermocouple measurements are within +/–35 K at the sample position up to 800 K and within +90 K between 800 and 1400 K when using a standard seat combination of cBN and WC. Isothermal compression at high temperatures can be achieved by employing a remote membrane control system. Importantly, the advantage of the GRHDAC is demonstrated through the study of geophysical processes in the Earth’s crust and upper mantle region.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
One Structure, Two Elements—LuGe 2 Superconductor vs Ordinary Metallic Conductor LuSn 2 . A Case Study on How Site-Selective Germanium for Tin Atom Substitution Leads to Modulating of the Charge Distribution
The substitution of chemically similar elements in a given crystal structure is an effective way to enhance physical properties, but the understanding on such improvements is usually impeded because the substitutions are random, and the roles of the different atoms cannot be distinguished by crystallographic symmetry. Herein, we provide a detailed crystallographic analysis and property measurements for the continuous solid solutions LuGe x Sn 2–x (0 < x < 2). The results show that there is no apparent change of the global symmetry, with the end-members LuGe 2 and LuSn 2 , as well as the intermediate LuGe x Sn 2–x compositions adopting the ZrSi 2 type structure (space group Cmcm, Pearson index oC12). Yet, the refinements of the crystal structures from single-crystal X-ray diffraction data show that Ge–Sn atom substitutions are not random, but occur preferentially at the zig-zag chain. The patterned distribution of two group 14 elements leads to a significant variation in chemical bonding and charge ordering within the other structural fragment, the 2D square nets, thereby resulting in tuned electron transport. The enhancement is greater than the typical Bloch-Gruneisen model, and more akin to the parallel-resistor model. Magnetization measurements on single crystals show bulk superconductivity in all LuGe x Sn 2–x samples with shielding fractions as high as 90%. Specific heat data confirm the effect to originate from residual metallic tin in the material, indicating that Sn atom substitutions in the 2D square nets cause disruptions of the hypervalent bonding and local anisotropy, which ultimately leads to vanishing of the superconducting state in the end-member LuGe 2 . This work sheds light on how the complexity in chemical interactions by two different carbon congeners leads to changes in the physical properties and how they can be correlated with the induced charge distribution. Furthermore, these studies also provide a general approach to modulation of charge density, and thus, of emerging physical properties in other classes of intermetallic systems based on the main-group elements of groups 13 to 15.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Growth of PrCo 2 single crystals with a Boron Nitride crucible
Single crystals of PrCo 2 have been grown from flux starting from Pr 0.44 Co 0.56 that was synthesized by arc melting of stoichiometric mixtures of the elements. The Pr 0.44 Co 0.56 ingot was loaded in a Boron Nitride (BN) crucible and sealed inside a quartz tube under vacuum. The quartz ampoule was heated to 1203 K, and then slowly cooled down to 923 K at a rate of 2 K/h. The obtained crystals have octahedral shapes and are of cubic C15 Laves phase structure confirmed by room temperature powder and single-crystal X-ray diffraction measurements. Magnetic susceptibility data show the Curie temperature T C = 46.7 K. The experimental value of saturation magnetization M s = 3.2 μ B /f.u is consistent with our theoretical calculations.
36 MATERIALS SCIENCE↗
Synthesis and Characterization of Layered Actinide (U, Np, Pu) Oxide and Hydroxide Phases
Systematic structural comparisons across the early actinides remain limited by the scarcity of well-defined transuranic layered oxide and oxyhydroxide phases. Here, we report the synthesis and single-crystal characterization of new layered actinide compounds spanning U, Np, and Pu obtained under mild hydrothermal conditions in concentrated alkali hydroxide media. These include hydrated oxides α-Cs 2 U 2 O 7 •0.5H 2 O and Rb 2 An 2 O 7 •0.5H 2 O (An = Np, Pu), oxy-hydroxides Rb 6 [(AnO 2 ) 6 O 8 (OH) 2 ]•xH 2 O x = 0, 0.5 (An = U, Np) and Rb 4 [(UO 2 ) 5 O 6 (OH) 2 ]•2H 2 O, as well as nitrate-intercalated compounds Cs 6 [(AnO 2 ) 3 O 4 (OH) 2 ](NO 3 ) 2 (An = Np, Pu). Single-crystal X-ray diffraction studies reveal extended two-dimensional architectures constructed from edge- and vertex-sharing actinyl polyhedra, with systematic evolution in equatorial coordination, hydration, and anionic sheet topology across the U–Np–Pu series. Incorporation of nitrate anions within the interlayer region of Cs 6 [(AnO 2 ) 3 O 4 (OH) 2 ](NO 3 ) 2 establishes a previously unobserved structural motif in layered transuranic oxyhydroxides, demonstrating an additional pathway for anion-mediated framework stabilization. Correlation of crystallographic metrics with single-crystal Raman spectroscopy provides new vibrational benchmarks linking differences in An═O yl bond lengths to the equatorial coordination and the interstitial cations. These findings expand the structural hierarchy of layered actinide materials and address clarifying periodic trends governing topology, bonding, and vibrational signatures in high-valent 5ƒ oxide systems.
actinides↗