Classification of heavy metal fluorides. Fluorides with a body-centered cubic cationic sublattice (Rhombododecahedral complex)Borisov, S.; Bliznyuk, N.; Kuklina, E.
doi: 10.1007/BF02578277pmid: N/A
The structures of some binary and ternary fluorides with Rb, Cs, K, Na, In, Tr, Te, U, Th, etc., are analyzed, which belong to cubic, tetragonal, orthorhombic, and monoclinic crystal systems and have a cationic sublattice with a more or less deformed cubic I-cell. Six families of planes, most densely populated by cations, are oriented in the sublattice as {110} rhombododecahedral faces. Their intersection points determine cation positions. When the sublattice sites are populated by cations of different types, there is a tendency toward mutual isolation of high-charged cations. The interplanar distances between rhombododecahedral planes relate to those between {200} cubic planes as 1∶0.71, serving to diagnose the presence of an I-subcell. The form of the polyhedron cut out by close-packed cation planes is found to be comparable to the first Brillouin zone.
Synthesis of ternary potassium, magnesium, and zirconium molybdates. The crystal structure of K5(Mg0.5Zr1.5)·(MoO4)6Klevtsova, R.; Bazarova, Zh.; Glinskaya, L.; Alekseev, V.; Arkhincheeva, S.; Bazarov, B.; Klevtsov, P.; Fedorov, K.
doi: 10.1007/BF02578278pmid: N/A
Three (5∶1∶3, 1∶1∶1, and 2∶1∶6) ternary phases were discovered in the K2MoO4−AMoO4−Zr(MoO4)2 system, where A is Mg or Mn. For A=Mg, we have synthesized 5∶1∶3 single crystals and determined their crystal structure from X-ray diffraction data (a CAD-4 automatic diffractometer, MoKα radiation, 1166 F(hkl), and R=0.026). The compound crystallizes in the trigonal system with space group R3c, a=10.576(1), c=37.511(3), Å, Z=6, dcalc=3.576, and dmsd=3.54 g/cm3. The structure is a three-dimensional composite framework of alternating Mo tetrahedra and (Mg, Zr) octahedra, which are linked via the common O vertices. Potassium atoms of three kinds are located in large framework cavities. Their polyhedra (ten-vertex polyhedra and a cubeoctahedron) are linked together by common faces and edges to form infinite zigzag columns of a large section. When solving the structure, we refined the composition of the crystals and the distribution of Mg2+ and Zr4+ cations in the M(1) and M(2) positions resulting in the formula above.
Computational modeling of amorphous silica. 2. Modeling the initial structures. AerosilKhavryuchenko, V.; Sheka, E.
doi: 10.1007/BF02578279pmid: N/A
A qualitative algorithm for constructing large clusters of aerosil model structures is used. According to this algorithm and the classification of amorphous silicas, aerosil is classified with tectosilicas, which are characterized by close packing of silicon-oxygen tetrahedra. Two quantitative algorithms for constructing large close-packed clusters are proposed. The structures of the clusters having from 10 to 24 silicon atoms, completely optimized by quantum chemical methods, were obtained. Small, medium, and large clusters for modeling the local and collective properties of atomic and functional group packing in the aerosil structure are distinguished.
Computational modeling of amorphous silica. 3. Modeling the initial structures. Silica gelKhavryuchenko, V.; Sheka, E.
doi: 10.1007/BF02578280pmid: N/A
A qualitative algorithm for construction of large clusters of silica gel model structures is used. According to this algorithm and in line with our classification of dispersive silicas, silica gel is regarded as cyclosilica, which is characterized by loose packing of the cycles of silicon-oxygen tetrahedra. A model of silica gel structure is proposed, where the primary structural fragments are hollow frameworks with a network surface. The units of the surface network are formed by nonplanar [SiO4] chain cycles of various sizes. This structural model makes it possible to explain the peculiarities of the vibration spectra of the framework, hydroxyl, and aqueous components of silica gels.
Computational modeling of amorphous silica. 4. Modeling the initial structures. AerogelKhavryuchenko, V.; Sheka, E.
doi: 10.1007/BF02578281pmid: N/A
A qualitative classification algorithm for constructing large clusters of aerogel model structures is used. According to this algorithm, aerogel is classified with polysilicas characterized by a packing of long chains of silicon-oxygen tetrahedra. A model of the aerogel structure is suggested, according to which aerogel is described as a set of cross-linked chains forming double or more complex ribbons. This model is in agreement with the conclusions drawn from analysis of the vibration spectra of its components.
New examples of mixed-ligand bis(hexafluoroacetylacenonato)copper(II) complexes with 3-imidazoline nitroxide radicals at a Cu(C5HF6O2)2∶L=3∶2 ratio (L2=C14H19N2O, L3=C13H17N2O3)Pervukhina, N.; Podberezskaya, N.
doi: 10.1007/BF02578282pmid: N/A
The crystal structures of two (hexafluoroacetylacetonato)copper(II) complexes with 3-imidazoline nitroxide radicals, [Cu(C5HF6O2)2]3 (C14H19N2O)2 (I) and [Cu(C5HF6O2)2]3 (C13H17N2O3)2 (II), have been determined. The compounds are triclinic (PI, Z=1) with a=8.730(2), b=10.357(2), c=21.996(5) Å, α=103.24(2), β=94.03(2), γ=95.04(2)0, V=1920(1) Å3 for I and a=8.679(2), b=14.769(4), c=15.368(4) Å, α=85.58(2), β=96.25(1), γ=104.60(1)0, V=1893(1) Å3 for II. Complexes I and II are molecular. The trinuclear molecules are centrosymmetric relative to the Cu(1) atom. The coordination polyhedron of Cu(1) is a square bipyramid formed by the O atoms of the hfac anions and nitroxide radicals (average Cu−Ohfac 1.92(1) for I and 1.93(1) Å for II; Cu−ON−O 2.47(1) for I and 2.56(1) Å for II). The coordination polyhedron of Cu(2) is a trigonal bipyramid formed by the O atoms of the hfac anions (Cu−Ohfac 1.91(1)–2.12(1) for I and 1.91(1)–2.09(1) Å for II) and an imine N atom of the radical (Cu(2)−N(2) 2.00(1) for I and 2.03(1) Å for II). The molecules are linked by van der Waals forces.
Aminoguanidinium cations and the square-bipyramidal hexachlorocuprate(II) anion in the (CH8N4)2[CuCl6] crystal structureRomanenko, G.; Savelyeva, Z.; Podberezskaya, N.; Alekseev, V.; Larionov, S.
doi: 10.1007/BF02578283pmid: N/A
Synthesis and structure of a novel thermochromic complex (CH8N4)2[CuCl6] are reported. X-ray analysis of the compound was carried out for a single crystal 0.4×0.2×0.05 mm in size (a bright-yellow plate). The monoclinic unit cell parameters are a=7.167(1), b=15.561(3), c=7.328(1) Å, β=118.73(3)°, V=716.7(2) Å3, space group P21, Z=2 (CH8N4)2[CuCl6] dcalc=1.99 g/cm3, μ(MoKα)=2.65 mm−1, R=0.0264, and Rw=0.0290 for 1411 Ihkl>2σI.
Clathrate formation in the tetraisoamylammonium propionate-water systemTerekhova, I.; Bogatyryov, V.; Dyadin, Yu.
doi: 10.1007/BF02578285pmid: N/A
In this paper we examine clathrate formation in the tetraisoamylammonium propionate-water binary system. We have found formation of four polyhydrates, two of which are metastable over the whole temperature range studied. All polyhydrate crystals were isolated and their compositions and densities determined; for (i-C5H11)4NC2H5COO·36.5H2O, unit cell parameters were additionally found. The results are compared with data for tetra-n-butylammonium carboxylate polyhydrates, and the structure of the title compounds is suggested. It is confirmed that the isoamyl radical stabilizes the tetradecahedral void of the clathrate hydrate framework better than the n-butyl radical.
Crystal structure of di (1-n-dodecylpyridine) decahydro-closo-decaborate(2-) (C5H5N-C12H25)2[B10H10]Virovets, A.; Vakulenko, N.; Volkov, V.; Podberezskaya, N.
doi: 10.1007/BF02578286pmid: N/A
Using X-ray analysis, we have determined the crystal structure of di(1-n-dodecylpyridine) decahydrocloso-decaborate(2-), (py-C12H25)2[B10H10] (I), a yellow salt-like substance obtained by reaction of (py-C12H25)Br and K2[B10H10] in an aqueous solution. Compound I melts at 1250 without decomposition and luminesces under ultraviolet radiation (λmax=555 nm at 298 K). In I, quaternary pyridine bases, containing a hydrocarbon radical with the C12 chain, are combined with the closo-cluster hydroborate anion [B10H10]2-. This results in a charge transfer structure having shortened nonvalent (equatorial B) H.…H(C of pyridine) contacts of 2.41(8) Å. Crystals I are orthorhombic with a=8.584 (1), b=7.739(1), c=31.183(5) Å, Vcell=2071.4(5) Å3, space group Pnmm, Z=2, dcalc=0.986 g/cm3 (a Syntex P21 automatic diffractometer, λCUKα, Nmsd/used=1654/711, Raniso=0.076, Rw=0.080, w=1/(σ(Fobs)2+0.0007·F
obs
2
). Substantial changes are observed in the vibration range of the valent B−H bonds in the IR spectrum of I as compared to that of pure ionic K2[B10H10], confirming the interaction.