Finding the Order in Complexity: The Electronic Structure of 14-1-11 Zintl Compounds

Yb14MnSb11 and Yb14MgSb11 have rapidly risen to prominence as high-performing p-type thermoelectric materials for potential deep space power generation. However, the fairly complex crystal structure of 14-1-11 Zintl compounds renders the interpretation of the electronic band structure obscure, making it difficult to chemically guide band engineering and optimization efforts. In this work, we delineate the valence balanced Zintl chemistry of A14MX11 compounds (A = Yb, Ca; M = Mg, Mn, Al, Zn, Cd; X = Sb, Bi) using molecular orbital theory analysis. By analyzing the electronic band structures of Yb14MgSb11 and Yb14AlSb11 , we show that the conduction band minimum is composed of either an antibonding molecular orbital originating from the (Sb3)7− trimer, or a mix of atomic orbitals of A, M, and X. The singly degenerate valence band is comprised of non-bonding Sb p-z orbitals primarily from the Sb atoms in the (MSb4)m- tetrahedra and the of isolated Sb atoms distributed throughout the unit cell. Such a chemical understanding of the electronic structure enables strategies to engineer electronic properties (e.g., the band gap) of A14MX11 compounds.

Lead-substituted barium hexaferrite for tunable terahertz optoelectronics

Due to their outstanding dielectric and magnetic properties, hexaferrites are attracting ever-increasing attention for developing electronic components of next-generation communication systems. The complex crystal structure of hexaferrites and the critical dependences of their electric and magnetic properties on external factors, such as magnetic/electric fields, pressure, and doping, open ample opportunities for targeted tuning of these properties when designing specific devices. Here we explored the electromagnetic properties of lead-substituted barium hexaferrite, Ba1−xPbxFe12O19, a compound featuring an extremely rich set of physical phenomena that are inherent in the dielectric and magnetic subsystems and can have a significant effect on its electromagnetic response at terahertz frequencies. We performed the first detailed measurements of the temperature-dependent (5–300 K) dielectric response of single-crystalline Ba1−xPbxFe12O19 in an extremely broad spectral range of 1 Hz–240 THz. We fully analyzed numerous phenomena with a corresponding wide distribution of specific energies that can affect the terahertz properties of the material. The most important fundamental finding is the observation of a ferroelectric-like terahertz excitation with an unusual temperature behavior of its frequency and strength. We suggest microscopic models that explain the origin of the excitation and its nonstandard temperature evolution. Several narrower terahertz excitations are associated with electronic transitions between the fine-structure components of the Fe2+ ground state. The discovered radio-frequency relaxations are attributed to the response of magnetic domains. Gigahertz resonances are presumably of magnetoelectric origin. The obtained data on diverse electromagnetic properties of Ba1−xPbxFe12O19 compounds provide information that makes the entire class of hexaferrites attractive for manufacturing electronic devices for the terahertz range.

A Novel Tetranuclear Silver Compound with bis(3,5-dimethylpyrazol-1-yl)acetate: a Simple Synthesis Yielding Complex Crystal Structure

A novel tetranuclear silver coordination compound with the formula [Ag4(bdmpza)4]·10H2O (bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate) was synthesized by a reaction between an aqueous solution of silver nitrate and an aqueous solution prepared by bis(3,5-dimethylpyrazol-1-yl)acetic acid and potassium hydroxide (1:1 molar ratio). The obtained compound was characterized by elemental analysis, coupled thermogravimetric–mass spectrometry analysis, vibrational IR spectroscopy, and its crystal structure was determined by single-crystal X-ray diffraction method. Furthermore, the obtained crystal structure was additionally evaluated by Hirshfeld surface analysis.

Complex Crystal Structure Determination and in vitro Anti–non–small Cell Lung Cancer Activity of Hsp90N Inhibitor SNX-2112

SNX-2112, as a promising anticancer lead compound targeting heat shock protein 90 (Hsp90), absence of complex crystal structure of Hsp90N-SNX-2112 hindered further structural optimization and understanding on molecular interaction mechanism. Herein, a high-resolution complex crystal structure of Hsp90N-SNX-2112 was successfully determined by X-ray diffraction, resolution limit, 2.14 Å, PDB ID 6LTK, and their molecular interaction was analyzed in detail, which suggested that SNX-2112 was well accommodated in the ATP-binding pocket to disable molecular chaperone activity of Hsp90, therefore exhibiting favorable inhibiting activity on three non–small cell lung cancer (NSCLC) cell lines (IC50, 0.50 ± 0.01 μM for A549, 1.14 ± 1.11 μM for H1299, 2.36 ± 0.82 μM for H1975) by inhibited proliferation, induced cell cycle arrest, and aggravated cell apoptosis. SNX-2112 exhibited high affinity and beneficial thermodynamic changes during the binding process with its target Hsp90N confirmed by thermal shift assay (TSA, ΔTm, and −9.51 ± 1.00°C) and isothermal titration calorimetry (Kd, 14.10 ± 1.60 nM). Based on the complex crystal structure and molecular interaction analysis, 32 novel SNX-2112 derivatives were designed, and 25 new ones displayed increased binding force with the target Hsp90N verified by molecular docking evaluation. The results would provide new references and guides for anti-NSCLC new drug development based on the lead compound SNX-2112.