Composition Determination of Heterometallic Trinuclear Clusters via Anomalous X-ray and Neutron Diffraction.

Anomalous X-ray diffraction (AXD) and neutron diffraction can be used to crystallographically distinguish between metals of similar electron density. Despite the use of AXD for structural characterization in mixed metal clusters, there are no benchmark studies evaluating the accuracy of AXD toward assessing elemental occupancy in molecules with comparisons with what is determined via neutron diffraction. We collected resonant diffraction data on several homo and heterometallic clusters and refined their anomalous scattering components to determine metal site occupancies.

Reengineering of Donor-Acceptor-Donor Structured Near-Infrared II Aggregation-Induced Emission Luminogens for Starving-Photothermal Antitumor and Inhibition of Lung Metastasis.

Electron acceptor possessing strong electron-withdrawing ability and exceptional stability is crucial for developing donor-acceptor-donor (D-A-D) structured aggregation-induced emission luminogens (AIEgens) with second near-infrared (NIR-II) emission. Although 6,7-diphenyl-[1,2,5] thiadiazolo [3,4-] quinoxaline (PTQ) and benzobisthiadiazole (BBT) are widely employed as NIR-II building blocks, they still suffer from limited electron-withdrawing capacity or inadequate chemo-stability under alkaline conditions. Herein, a boron difluoride formazanate (BFF) acceptor is utilized to construct NIR-II AIEgen, which exhibits a better overall performance in terms of NIR-II emission and chemo-stability compared to the PTQ- and BBT-derived fluorophores.

Floristic analyses of Shandong peninsula and adjacent areas indicate the barrier effect of the Yellow river on floristic diversity.

The Shandong Peninsula, the largest peninsula in China, is situated at the estuary of the Yellow River and is bordered by both the Bohai Sea and the Yellow Sea. This region is renowned for its rich plant diversity. However, the historical origins of these plant species remain poorly understood.

Cu site differentiation in tetracopper(i) sulfide clusters enables biomimetic NO reduction.

Copper clusters feature prominently in both metalloenzymes and synthetic nanoclusters that mediate catalytic redox transformations of gaseous small molecules. Such reactions are critical to biological energy conversion and are expected to be crucial parts of renewable energy economies. However, the precise roles of individual metal atoms within clusters are difficult to elucidate, particularly for cluster systems that are dynamic under operating conditions.

Development of a scalar-based geometric parameterization approach for the crystal structure landscape of dithienylethene-based crystalline solids.

Dithienylethenes (DTEs) are a promising class of organic photoswitches that can be used to create crystalline solids with properties controlled by light. However, the ability of DTEs to adopt multiple conformations, only one of which is photoactive, complicates the rational design of these materials. Herein, the synthesis and structural characterization of 19 crystalline solids containing a single DTE molecule are described.

Structure-Based GC Investigation Sheds New Light on ITS2 Evolution in Species.

Guanine and cytosine (GC) content is a fundamental component of genetic diversity and essential for phylogenetic analyses. However, the GC content of the ribosomal internal transcribed spacer 2 (ITS2) remains unknown, despite the fact that ITS2 is a widely used phylogenetic marker. Here, the ITS2 was high-throughput sequenced from 29 species, and their GC contents were comparatively investigated in the context of ITS2's characteristic secondary structure and concerted evolution.

Revealing redox isomerism in trichromium imides by anomalous diffraction.

In polynuclear biological active sites, multiple electrons are needed for turnover, and the distribution of these electrons among the metal sites is affected by the structure of the active site. However, the study of the interplay between structure and redox distribution is difficult not only in biological systems but also in synthetic polynuclear clusters since most redox changes produce only one thermodynamically stable product. Here, the unusual chemistry of a sterically hindered trichromium complex allowed us to probe the relationship between structural and redox isomerism.

High-Resolution In-Situ Synchrotron X-Ray Studies of Inorganic Perovskite CsPbBr : New Symmetry Assignments and Structural Phase Transitions.

Perovskite photovoltaic ABX systems are being studied due to their high energy-conversion efficiencies with current emphasis placed on pure inorganic systems. In this work, synchrotron single-crystal diffraction measurements combined with second harmonic generation measurements reveal the absence of inversion symmetry below room temperature in CsPbBr . Local structural analysis by pair distribution function and X-ray absorption fine structure methods are performed to ascertain the local ordering, atomic pair correlations, and phase evolution in a broad range of temperatures.

Intertwined density waves in a metallic nickelate.

Nickelates are a rich class of materials, ranging from insulating magnets to superconductors. But for stoichiometric materials, insulating behavior is the norm, as for most late transition metal oxides. Notable exceptions are the 3D perovskite LaNiO, an unconventional paramagnetic metal, and the layered Ruddlesden-Popper phases RNiO, (R = La, Pr, Nd).

Materializing rival ground states in the barlowite family of kagome magnets: quantum spin liquid, spin ordered, and valence bond crystal states.

The spin- kagome antiferromagnet is considered an ideal host for a quantum spin liquid (QSL) ground state. We find that when the bonds of the kagome lattice are modulated with a periodic pattern, new quantum ground states emerge. Newly synthesized crystalline barlowite (Cu(OH)FBr) and Zn-substituted barlowite demonstrate the delicate interplay between singlet states and spin order on the spin- kagome lattice.

Pressure-Thresholded Response in Cylindrically Shocked Cyclotrimethylene Trinitramine (RDX).

We demonstrate a strongly thresholded response in cyclotrimethylene trinitramine (RDX) when it is cylindrically shocked using a novel waveguide geometry. Using ultrafast single-shot multi-frame imaging, we demonstrate that <100 μm diameter single crystals of RDX embedded in a polymer host deform along preferential planes for >100 ns after the shock first arrives in the crystal. We use in situ imaging and time-resolved photoemission to demonstrate that short-lived chemistry occurs with complex deformation pathways.

III-V Clathrate Semiconductors with Outstanding Hole Mobility: CsInSb and GaSb ( = Cs, Rb).

Three novel unconventional clathrates with unprecedented III-V semiconducting frameworks have been synthesized: CsInSb, CsGaSb, and RbGaSb. These clathrates represent the first examples of tetrel-free clathrates that are completely composed of main group elements. All title compounds crystallize in an ordered superstructure of clathrate-I in the 3̅ space group (No.

Site-Specific Structure at Multiple Length Scales in Kagome Quantum Spin Liquid Candidates.

Realizing a quantum spin liquid (QSL) ground state in a real material is a leading issue in condensed matter physics research. In this pursuit, it is crucial to fully characterize the structure and influence of defects, as these can significantly affect the fragile QSL physics. Here, we perform a variety of cutting-edge synchrotron X-ray scattering and spectroscopy techniques, and we advance new methodologies for site-specific diffraction and L-edge Zn absorption spectroscopy.

Crystal structures and phase relationships in magnetostrictive Tb Dy Co system.

The crystal structures and phase relationships of Tb Dy Co alloys with 0  ⩽  x  ⩽  1 were investigated by synchrotron-based high-resolution x-ray powder diffraction. Three different crystal structures are observed in the system: all the compositions show cubic structure with space group [Formula: see text] at temperatures above the Curie temperature T the Tb-rich side sample shows a rhombohedral structure with space group [Formula: see text] and the Dy-rich side sample has a tetragonal [Formula: see text] space group. In situ measurements on the intermediate compound TbDyCo show a rhombohedral to tetragonal structural transition, and the two phases coexist from 99 K to 111 K, where the so-called magnetic morphotropic phase boundary (MPB) is found.

Exposing the inadequacy of redox formalisms by resolving redox inequivalence within isovalent clusters.

In this report we examine a family of trinuclear iron complexes by multiple-wavelength, anomalous diffraction (MAD) to explore the redox load distribution within cluster materials by the free refinement of atomic scattering factors. Several effects were explored that can impact atomic scattering factors within clusters, including 1) metal atom primary coordination sphere, 2) M-M bonding, and 3) redox delocalization in formally mixed-valent species. Complexes were investigated which vary from highly symmetric to fully asymmetric by Fe Mössbauer and X-ray diffraction to explore the relationship between MAD-derived data and the data available from these widely used characterization techniques.

Ligand-Based Control of Single-Site vs. Multi-Site Reactivity by a Trichromium Cluster.

The trichromium cluster ( L)Cr (thf) ([ L] =[1,3,5-C H (NC H -o-NSi BuMe ) ] ) exhibits steric- and solvation-controlled reactivity with organic azides to form three distinct products: reaction of ( L)Cr (thf) with benzyl azide forms a symmetrized bridging imido complex ( L)Cr (μ -NBn); reaction with mesityl azide in benzene affords a terminally bound imido complex ( L)Cr (μ -NMes); whereas the reaction with mesityl azide in THF leads to terminal N-atom excision from the azide to yield the nitride complex ( L)Cr (μ -N). The reactivity of this complex demonstrates the ability of the cluster-templating ligand to produce a well-defined polynuclear transition metal cluster that can access distinct single-site and cooperative reactivity controlled by either substrate steric demands or reaction media.

Electron Cartography in Clusters.

Deconvoluting the atom-specific electron density within polynuclear systems remains a challenge. A multiple-wavelength anomalous diffraction study on four clusters that share the same [Co Se ] core was performed. Two cluster types were designed, one having a symmetric ligand sphere and the other having an asymmetric ligand sphere.

Synthesis, Structure, and Electrical Properties of the Single Crystal BaCuAs.

Single crystals of clathrate-I BaCuAs have been synthesized and their structure and electronic properties determined using synchrotron-based X-ray diffraction and first-principles calculations. The structure is confirmed to be Pm3̅ n (No. 223), with lattice parameter a = 10.

η-SO Linkage Photoisomer of an Osmium Coordination Complex.

We report the discovery of an η-SO linkage photoisomer in the osmium pentaammine coordination complex, [Os(NH)(SO)][Os(NH)(HSO)]Cl (1). Its dark- and light-induced crystal structures are determined via synchrotron X-ray crystallography, at 100 K, where the photoinduced state is metastable in a single crystal that has been stimulated by 505 nm light for 2.5 h.