Open-Framework Germanate Built from the Hexagonal Packing of Rigid Cylinders

Olivine Crystal Structure-Directed Twinning in Iron Germanium Sulfide (Fe2GeS4) Nanoparticles

Understanding the microstructure of complex crystal structures is critical for controlling material properties in next-generation devices. Synthetic reports of twinning in bulk and nanostructured crystals with detailed crystallographic characterization are integral for advancing systematic studies of twinning phenomena. Herein, we report a synthetic route to controllably twinned olivine nanoparticles. Microstructural characterization of Fe₂GeS₄ nanoparticles via electron microscopy (imaging, diffraction, and crystallographic analysis) demonstrates the formation of triplets of twins, or trillings. We establish synthetic control over the particle crystallinity and crystal growth. We describe the geometrical basis for twin formation, hexagonal pseudosymmetry of the orthorhombic lattice, and rank all of the reported olivine compounds according to this favorability to form twins. The work in this study highlights an area ripe for future exploration with respect to the advancement of solution-phase synthetic approaches that can control microstructure in compositionally complex, technologically relevant structures. Finally, we discuss the potential implications for olivine properties and performance in various applications.

Synthesis of Organosilyl-Functionalized Cage-Type Germanoxanes Containing Fluoride Ions

Eight corners of a double-four ring cage-type germanoxane, containing a fluoride ion, were successfully silylated by the combination of chlorosilanes and silazanes. Three different silyl groups, trimethylsilyl, dimethylsilyl, and dimethylvinylsilyl, were attached on the corners of germanoxane cage. The solubility and reactivity of the cage modified with dimethylvinylsilyl groups were significantly increased, allowing for further reaction. Hydrosilylation reaction between dimethylvinylsilylated cage geramanoxanes and dimethylsilylated cage siloxanes afforded porous solids. Functionalization of the corners of germanoxanes with silyl groups should provide valuable building blocks in various functional materials.

Application of X-ray Diffraction and Electron Crystallography for Solving Complex Structure Problems

All crystalline materials in nature, whether inorganic, organic, or biological, macroscopic or microscopic, have their own chemical and physical properties, which strongly depend on their atomic structures. Therefore, structure determination is extremely important in chemistry, physics, materials science, etc. In the past centuries, many techniques have been developed for structure determination. The most widely used one is X-ray crystallography (single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD)), and it remains the most important technique for structure determination of crystalline materials. Although SCXRD and PXRD are successful in many cases, a number of reasons limit their applications, such as SCXRD for nanosized crystals, intergrowth, and defects and PXRD for complex structures, multiphasic samples, impurities, peak overlaps, etc. Another most valuable technique for structure determination is electron crystallography (EC). With the electron as a probe, EC alone can also be used for structure determination, especially for crystals that are too small to be studied by SCXRD or too complex for PXRD. As electrons interact much more strongly with matter than X-rays do, both electron diffraction (ED) patterns and high-resolution transmission electron microscopy (HRTEM) images can be obtained from nanosized crystals. However, collecting a complete set of ED patterns or recording a good HRTEM image requires considerable expertise on the operation of electron microscopes and crystallography. The strong interactions between electrons and materials can also lead to dynamical effects and beam damage. These difficulties make structure determination from ED patterns and HRTEM images not straightforward. Recently, two three-dimensional (3D) electron diffraction techniques, automated electron diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed, which perform the data collection in an automated manner. Although the dynamical effects in the newly developed 3D electron diffraction techniques (ADT, RED) are reduced significantly, for some structures there are still problems with obtaining an initial model because of beam damage. The X-ray diffraction and EC methods discussed above are both powerful techniques but have their own limitations. In many complicated cases, one technique alone is not enough to solve the crystal structure, and different techniques that supply complementary structural information have to support each other for the complete structure determination. In this Account, we provide a summary of the advantages and disadvantages of X-ray diffraction (PXRD and SCXRD) and EC (HRTEM and ED) for structure determination and include a review of applications of X-ray diffraction and EC for solving complex structure problems such as peak overlap, impurities, pseudosymmetry and twinning, disordered frameworks, locating guests, aperiodic structures, etc. Some of the latest advances in structure determination are also presented briefly, namely, revealing hydrogen positions by ED, protein crystal structure solution by 3D electron diffraction, and structure determination using an X-ray free electron laser (XFEL).

Interrupted silicogermanate with 10-ring channels: synthesis and structure determination by combining rotation electron diffraction and powder X-ray diffraction

Structure determination of silicogermanate with sti layers pillared by D4R/Ge₇ units by rotation electron diffraction and powder X-ray diffraction.

SU-79: a novel germanate with 3D 10- and 11-ring channels templated by a square-planar nickel complex

An open-framework germanate SU-79 was synthesized using nickel complex and amine as the templates. The crystal structure was solved by the combination of rotation electron diffraction (RED) and synchrotron single crystal X-ray diffraction.

Solving complex open-framework structures from X-ray powder diffraction by direct-space methods using composite building units

The crystal structure of a novel open-framework gallogermanate, SU-66 {|(C6H18N2)18(H2O)32|[Ga4.8Ge87.2O208]}, has been solved from laboratory X-ray powder diffraction (XPD) data by using a direct-space structure solution algorithm and local structural information obtained from infrared (IR) spectroscopy. IR studies on 18 known germanates revealed that the bands in their IR spectra were characteristic of the different composite building units (CBUs) present in the structures. By comparing the bands corresponding to Ge—O vibrations in the IR spectra of SU-66 with those of the 18 known structures with different CBUs, the CBU of SU-66 could be identified empirically as the Ge10(O,OH)27 cluster (Ge10). The unit cell and space group (extinction symbol P--a; a = 14.963, b = 31.593, c = 18.759 Å) were determined initially from the XPD pattern and then confirmed by selected-area electron diffraction. The structure of SU-66 was solved from the XPD data using parallel tempering as implemented in FOX [Favre-Nicolin & Černý (2002). J. Appl. Cryst. 35, 734–743] by assuming P21 ma symmetry and two Ge10 clusters in the asymmetric unit. Rietveld refinement of the resulting structure using synchrotron XPD data showed the framework structure to be correct and the space group to be Pmma. The framework has extra-large (26-ring) one-dimensional channels and a very low framework density of 10.1 Ge/Ga atoms per 1000 Å3. SU-66, with 55 framework atoms in the asymmetric unit, is one of the more complicated framework structures solved from XPD data. Indeed, 98% of the reflections were overlapping in the XPD pattern used for structure solution. Tests on other open-framework germanates (SU-62, SU-65, SU-74, PKU-12 and ITQ-37) for which the XPD data, unit cell, space group and IR spectra were available proved to be equally successful. In a more complex case (SU-72) the combination of FOX and powder charge flipping was required for structure solution.

Synthesis, Structure, and Characterization of Keggin-Type Germanate

A novel Keggin-type germanate, (NH4)9[Ge7O14F3]3·1.75H2O (I), is hydrothermally synthesized and structurally characterized by X-ray single-crystal diffraction, elemental analysis, XRD, and TG. (I) is tetragonal system with space group I4/mmm and unit cell:a=28.280(4) Å,c=24.881(5) Å,V=19899(6) Å3,Dc=1.632 g/cm3,μ(Mo Kα)=6.309 mm−1,Z=2,R1=0.1141for 2576 reflections withFo>2(Fo). Ge7O14F3entry is defined as the cluster including one octahedron, two edge-sharing triganol bipyramids, and four tetrahedra. Every Ge7O14F3entry links adjacent four Ge7O14F3entries by four tetrahedra. Twelve Ge7O14F3entries construct a cage with all octahedra of Ge7O14F3pointing inside, which can be simplified into Keggin-type cage through Ge7O14F3as the node. The solvent experiment proves that (I) is stable in the water and sensitive to base and acid. The result of XRD shows that the structural water of (I) is easily lost to drop the crystalline. The thermal study indicates that the Keggin-type cage of (I) begins to partly collapse at 200°C and finally changes into GeO2.

(C8H22N4Zn)2Ge7O14(OH)F3: a one-dimensional zinc germanate containing hollow columns with an 18-membered window

A new zinc germanate incorporating a tetradentate amine ligand has been synthesized by the solvothermal method and structurally characterized by single-crystal X-ray diffraction, solid-state (19)F NMR spectroscopy, thermal analysis, and IR spectroscopy. Its structure contains close-packed hollow columns with an 18-membered window, each of which contains six one-dimensional chains formed of Ge(7)X(19) (X = O, OH, F) clusters connected to zinc complexes.

Organically templated metal germanate: ionothermal synthesis of (C8H24N4)[NbOGe6O13(OH)2F]

A very rare organically templated niobium germanate was synthesized and structurally characterized by single-crystal X-ray diffraction. The crystal shows an intense second harmonic generation signal. It is the first example of the synthesis of organically templated metal germanate using an ionic liquid as a solvent.