Synthesis,structure, physical properties,and electronic structure of KGaSe2

The ternary gallium selenide KGaSe₂ has been synthesized by solid-state reactions and good quality crystal has been obtained. KGaSe₂ crystallizes in the monoclinic space group C2/c with cell dimensions of a = 10.878(2) Å, b = 10.872(2) Å, c = 15.380(3) Å, and β = 100.18(3)°. In the structure, adamantane like [Ga₄Se₁₀]⁸⁻ units are connected by common corners forming two-dimensional [GaSe₂]⁻ layers which are separated by K⁺ cations. KGaSe₂ exhibits congruent-melting behavior at around 965 °C. It is transparent in the range of 0.47–20.0 μm and has a band gap of 2.60(2) eV. From a band structure calculation, KGaSe₂ is a direct-gap semiconductor. The band gap is mainly determined by the [GaSe₂]⁻ layer.     

Synthesis,structure, electrical properties,and band structure calculations of TiAsTe

The new compound TiAsTe has been synthesized by the reaction of the elements in a LiCl/KCl flux at 923 K. The compound crystallizes with four formula units in space group Immm of the orthorhombic system in a cell at 153 K of a = 3.5730(8) A, b = 5.249(1) A, c = 12.794(3) A, V = 240.0(1) A(3). The structure, which is of the NbPS structure type, is a three-dimensional extended framework built from bicapped TiAs(4)Te(4) trigonal prisms. It may be considered to comprise infinity (2) [TiTe] slabs perpendicular to [001] that are interspersed with linear infinity (1)[As] chains running along [010]. The As-As distances alternate at 2.554(2) and 2.695(2) A. Electrical and thermopower measurements indicate that TiAsTe is an n-type metallic compound. Density functional theory calculations help rationalize the chemical bonding and physical properties.     

Crystal structure, electronic structure, and bonding properties of anhydrous nickel oxalate

The results of crystal structure determination and theoretical analysis of electronic structure and bonding properties in relation to thermal decomposition process in anhydrous nickel oxalate are presented. The details of the methods used in this analysis i.e., the Bader’s quantum theory of atoms in molecules and bond order models (as defined by Pauling, Bader, Cioslowski and Mixon—modified by Howard and Lamarche), applied to topological properties of the electron density, obtained from ab initio calculations carried out by Wien2k FP-LAPW package (full potential linearized augmented plane wave method), as well as Brown’s bond valence model (bond valences and strengths, and bond and crystal strains, calculated from experimental crystal structure data) are described. Nickel oxalate dihydrate was prepared by precipitation from water solutions of nickel nitrate (V) with oxalic acid at about 60 °C. The crystalline powder was filtered, washed, and dried at 80 °C on air. Anhydrous nickel oxalate sample was measured by XRD method applying Philips X’Pert Pro MD diffractometer equipped with MRI high temperature cell. Structural as well as qualitative and quantitative phase analyses were made by Phillips X’Pert HighScore Plus version 2.1 software with implemented full-pattern fit by means of Rietveld method. The detailed analysis of the obtained results shows that anhydrous nickel oxalate has monoclinic crystal structure (P2₁/c, sg 14), the carbon–carbon bond is the weakest one, and the process of thermal decomposition of this structure should begin with the breaking of this particular bond followed by nickel-oxygen bonds, which will lead to metallic nickel and carbon dioxide as final products, in agreement with the experiment. These results, supported by our earlier ones show clearly that such methods (topological and structural), when used simultaneously in analysis of the crystal structure and bonding properties, provide us with the additional insight into the behavior of given compound during thermal decomposition process and thus allow predicting and explaining of its most probable pathway.     

Synthesis, structure, optical properties, and electronic structure of NaLiCdS2

The new compound NaLiCdS₂ has been synthesized by the reaction of Cd and a Li₂S/S/Na₂S flux at 773 K. This compound, which has the Ce₂O₂S structure type, crystallizes with one formula unit in space group P3¯m1 of the trigonal system in a cell at T=153 K with a=4.1320(3) Å and c=6.8666(11) Å. The structure consists of two-dimensional layers stacked perpendicular to the [001] direction. The two-dimensional layers are formed by corner-sharing LiS₄ or CdS₄ tetrahedra. The Na atoms are between these layers. Li incorporation in the compound is confirmed by an SIMS chemical composition map and by ICP measurements. The Li and Cd atoms are disordered in the crystal structure. First-principles calculations show that the optical excitations arise primarily from S→Cd charge-transfer transitions at 1.0 eV (very weak) and 2.4 eV (strong). Calculations also indicate that Na contributions around the Fermi level are significant. Polarized single-crystal optical measurements indicate an indirect optical band gap of 2.37 eV for light perpendicular to the (001) crystal face, in good agreement with theory. The compound NaLiZnS₂ has also been synthesized and is found to be isostructural with NaLiCdS₂.     

Coumarins. Plants, structure, properties

The second chapter of the review contains information on 330 coumarins, arranged in Russian alphabetical order, with the names of the producing plants, structures, properties, melting points, specific rotations, spectral characteristics (UV, IR, NMR,¹³C NMR, etc.), and references to original papers and to unpublished work. For ease in locating these coumarins, they are listed in English alphabetical order in the table of contents below. ¹H and¹³C NMR spectra were taken in deuterochloroform ( scale, ppm, J values in Hz) except where otherwise noted.For the first part of this review, see Chemistry of Natural Compounds, 1998, No. 2, pp. 202–264.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 384–432, May–June, 1998.     

Azidocryptands-synthesis, structure, and complexation properties

Cryptands bearing an intraannular azido substituent have been synthesized and characterized spectroscopically. Their complexation properties were investigated by picrate extraction analysis. The oxygen-containing cryptands were found to be good ligands for alkali cations, with a preference for Li(+) and Na(+). The molecular structure of the complex with KBr was determined by X-ray crystallography. In this, the first structurally characterized complex of an aryl azide bound to a metal cation, the potassium cation was found to show ninefold coordination to four oxygen atoms and two nitrogen atoms of the crown ether moiety, to the bromide anion and to N1 of the azido group, as well as C1 of the benzene ring.     

Synthesis, crystal structure, and electronic structure of RbVSe2

RbVSe₂ has been synthesized at 773 K through the reaction of V and Se with a Rb₂Se₃ reactive flux. The compound crystallizes in the orthorhombic space group D_2h²⁴-Fddd with 16 formula units in a cell of dimensions , , and at . The structure possesses infinite one-dimensional chains of edge-sharing VSe₄ tetrahedra separated from the Rb⁺ ions. These chains distort slightly to chains. The V-V distance within these chains is 2.8362(4) Å. First-principles total energy calculations indicate that a non-magnetic configuration for the V³⁺ cations is the most stable.     

Synthesis, crystal structure, magnetic properties, and electronic structure of the new ternary vanadate CuMnVO4

A new magnetic oxide, CuMnVO4, was prepared, and its crystal structure was determined by single-crystal X-ray diffraction. The magnetic properties of CuMnVO4 were characterized by magnetic susceptibility and specific heat measurements, and the spin exchange interactions of CuMnVO4 were analyzed on the basis of spin-polarized electronic band structure calculations. CuMnVO4 contains MnO4 chains made up of edge-sharing MnO6 octahedra containing high-spin Mn2+ cations. Our work shows that CuMnVO4 undergoes a three-dimensional antiferromagnetic transition at approximately 20 K. Both the intrachain and interchain spin exchanges are antiferromagnetic, and the interchain spin exchange is not negligible compared to the intrachain spin exchange.     

Ferrocenylalkyl azoles: bioactivity,synthesis, structure

The toxicity of ferrocenylethyl benzotriazole ( 1 ) and other ferrocene compounds including ferrocenylmethyl benzimidazoles ( 4,5,6,11 ), ferricenium salts ( 3,9,10 ) and ferrocenylmethyl adenine ( 7 ), was studied. All ferrocene complexes under investigation showed low or medium toxicities. On the basis of an earlier model of chemical carcinogenesis, the antitumor activity of ferrocenylalkyl azoles 1, 8 and ferricenium salts 9, 10 was studied in vivo in the so‐called sub‐capsular test on human tumors. This effectiveness was compared with that of cisplatin. A series of ferrocenylalkyl azoles were synthesized by interacting azoles either with α‐hydroxyalkyl ferrocenes FcC(OH)R₁R₂ in organic solvent in the presence of aqueous HBF₄ in quantitative yields or with trimethyl(aminomethyl)ferrocene iodide in an aqueous‐basic medium in good yields. The X‐ray determinations of molecular and crystal structures of α‐(1‐benzotriazolyl)ethylferrocene ( 1 ) and α‐(1‐naphthatriazolyl)ethylferrocene ( 12 ) were performed. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis,structure, and properties of N-quinoxalylformazans

The first representatives of the previously unknown N-quinoxalylformazans were synthesized. Their chemical properties were investigated, and their structure and chromaticity are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1705–1707, December, 1973.     

Synthesis, structure, and toxicity of arylgermatranes

A series of tolylgermatranes were synthesized. Their structures and the length of the transannular N→Ge bond were determined. It was shown that arylgermatranes are less toxic than the corresponding silatranes.     

Cu4Mo6Se8: synthesis, crystal structure, and electronic structure of a new Chevrel phase structure type

Cu4Mo6Se8 has been synthesized by intercalation of Cu into Cu2Mo6Se8 at room temperature, and its crystal structure has been determined. This compound crystallizes in the triclinic space group P, with a = 6.7609(8) A, b = 6.8122(7) A, c = 7.9355(10) A, alpha = 70.739(4) degrees , beta = 72.669(4) degrees , gamma = 84.555(5) degrees , and Z = 1. Instead of residing in the voids between corners or edges of Mo6Se8 clusters as in the classic R Chevrel structure, the Cu atoms in Cu4Mo6Se8 fully occupy four sites between faces of two adjacent Mo6Se8 clusters. Thus, two of the six Mo atoms in each cluster do not have capping Se atoms from neighboring clusters. This represents a new triclinic structure type for Chevrel phases. In addition to the synthesis and crystal structure, we present and discuss results from electronic structure calculations using both extended Hückel and density functional theory. These calculations predict Cu4Mo6Se8 to be metallic. We also report results from Cu intercalation into Chevrel phase sulfides and tellurides. Preliminary experiments suggest that a telluride analogue of Cu4Mo6Se8 exists.