Double Zigzag Chains Research Articles

The framework topology of magnesiumaluminophosphate structure type 36

The crystal structure of MAPO-36 was solved and refined by combining information obtained bysynchrotron powder, Weissenberg single crystal (of an imperfect crystal), and electron and GuinierLenné powder diffraction. The powder pattern was indexed using a monoclinic cell ( C2/c) with a = 13.148, b = 21.577, and c = 5.164 Å and β = 91.84°. Powder patterns were calculated for hypothetical models having similar cell parameters and a match was finally achieved for a model related to but topologically different from cancrinite. The aluminophosphate-based molecular sieve structure type 36 is based on the 4.6.12 two-dimensional net ( gml) and the double zigzag chain ( zz), but unlike cancrinite, it has both radial and tangential chains around the 12-ring. This gives an elliptical channel with staggered annular side pockets. Even though it has smaller channels, these side pockets give it a greater adsorption capacity than that of AIPO-5.

Crystal structure of trans-C2SnO5 pentagonal bipyramidal dibutylbis(phenylacetato)tin(IV) hydrate

The Lewis acidity of tin in a diorganotin dicarboxylate is demonstrated in this first example of a 1/1 adduct of the ester with a neutral ligand. The structure of dibutyltin bisphenylacetate hydrate [(C4H9)2Sn(O2CCH2C6H5)2·H2O] has been determined from 1211 ∥F 0∥≥6σ∥F c ∥ MoKα reflections and refined to anR F of 0.061 [space groupP2/a witha=8.416(2),b=10.391(5),c=14.28(1) A,β=98.42(4)° andZ=2]. TheC α atoms [Sn-C 2.101(8) A; C-Sn-C 169.9(5)°] make up the apices and the Ocarboxylate [Sn-O 2.234(5), 2.439(7) A; O-Sn-O 55.7(2)°] and Owater [Sn-O 2.342(8) A] atoms the equatorial points of thetrans-C2SnO5 pentagonal bipyramid around the Sn atom. The molecular symmetry isC 2, and the Sn and Owater atoms lie along a crystallographic twofold axis. The aqua ligand forms donor H-bonds with neighboring carboxylato groups to link the molecules into a double zigzag chain running parallel toa.

Enumeration of Kekulé Structures for Multiple Zigzag Chains and Related Benzenoid Hydrocarbons

The benzenoid classes of multiple zigzag chains, A (n, m ), and incomplete multiple zigzag chains. A (n, m, l), are considered. Numerical numbers of Kekulé structures (K ) are given for n up to 5 and m up to 10. A recurrence relation is developed for the K numbers of A(n, m) with fixed values of n; a general formulation for arbitrary m values was achieved. Six new benzenoid classes are studied in connection with the application of the John-Sachs theorem to double zigzag chains. A new approach to the K enumeration is introduced by nonlinearly dependent recurrence relations. Finally a new type of combinatorial K formulas in terms of determinants and based on the John-Sachs theorem , is introduced. The new enumeration techniques are applied to multiple zigzag chains.

Crystal structure of lithium molybdenum purple bronze Li 0.9Mo 6O 17

The crystal structure of the molybdenum ternary oxide Li 0.9Mo 6O 17 is determined by single-crystal X-ray diffraction. The crystal is monoclinic with space group P2 1 m and the lattice constants are a = 12.762(2) Å, b = 5.523(1) Å, c = 9.499(1) Å, β = 90.61(1)°, Z = 2. Full-matrix least-squares refinement gives the final values of R( F) = 0.033 and R w ( F) = 0.066 for 3019 independent reflections. The unit cell contains six crystallographically independent molybdenum sites. One-third of the molybdenum atoms are located in oxygen tetrahedra, while the others are within oxygen octahedra. The structure is built up of slabs of the MoO 6 octahedra. Each slab consists of three layers of distorted ReO 3-type MoO 6 octahedra sharing corners. The structure is rather different from that of K 0.9Mo 6O 17, although the layered feature is still preserved. The lithium ions are located in the large vacant sites between the slabs. By the application of Zachariasen's bond length-bond strength relation to the observed MoO bonds, most of the conduction electrons are found to be located in the Mo(1) and Mo(4) octahedral sites which are associated in pairs to form the Mo(1)O(11)Mo(4)O(11) double zigzag chains extending along the b-axis. Therefore the structural properties are considered to lead to the highly anisotropic electronic transport.

The crystal structure of vanadium ditelluride V1+xTe2

Abstract Vanadium ditelluride, V1.04Te2, has a Cd(OH)2-type structure with unit cell dimensions ah = 3.638 A and ch = 6.582 A above the transition temperature Tt of 482 K. Below Tt the structure is monoclinic, space group C2 m , with cell dimensions am = 18.984 A(≈3ah√3), bm = 3.5947 A (≈ah), cm = 9.069 A (≈√(3a2h + c2h)), β = 134.62°. This low-temperature form is isostructural with NbTe2 and TaTe2 (which do not show a phase transition); the vanadium atoms form double zigzag chains with VV distances of 3.316 A, which distort the Te lattice. Complex diffraction patterns were observed due to the simultaneous occurrence of the distortion of the Cd(OH)2-type structure of vanadium ditelluride in three equivalent directions. Similar patterns were found for the Nb and Ta ditellurides.

The crystal structure of vanadium ditelluride, V 1+ xTe 2

Vanadium ditelluride, V 1.04Te 2, has a Cd(OH) 2-type structure with unit cell dimensions a h = 3.638 Å and c h = 6.582 Å above the transition temperature T t of 482 K. Below T t the structure is monoclinic, space group C2 m , with cell dimensions a m = 18.984 Å(≈3 a h√3), b m = 3.5947 Å (≈ a h), c m = 9.069 Å (≈√(3 a 2 h + c 2 h)), β = 134.62°. This low-temperature form is isostructural with NbTe 2 and TaTe 2 (which do not show a phase transition); the vanadium atoms form double zigzag chains with VV distances of 3.316 Å, which distort the Te lattice. Complex diffraction patterns were observed due to the simultaneous occurrence of the distortion of the Cd(OH) 2-type structure of vanadium ditelluride in three equivalent directions. Similar patterns were found for the Nb and Ta ditellurides.

Crystal structure of piperidinium hexathiotetra-arsenate

Crystals of [C5H12N]+2[As4S6]2– are orthorhombic, space group Imm2, with a= 10·25, b= 19·61, c= 5·97 A, Z= 2. The anion possesses a ‘basket’ structure in which the four arsenic atoms, and two of the sulphur atoms, lie on crystallographic mirror planes; the bond lengths are: As–As 2·579(12), As–S(terminal) 2·183(10), As–S(bridge) 2·302(11) and 2·231(8)A. The As4S62– anions are linked by double zig-zag chains of S ⋯ H–N hydrogen bonds parallel to the z axis. The structure was refined to R 0·129 for 660 independent reflections.

Structure and Phase Transition of Solid Hydrogen Sulphide

By electron diffraction and X-ray diffraction, the following facts are found. 1) A new tetragonal structure ( a =13.5 A and c =4.14 A) exists below a transformation point at about -168°C. 2) This structure changes (at -168°C) to the cubic structure which has already been known, after changing into a transient tetragonal structure ( a '=1/2· a and c '= c ). 3) The cubic structure shows a volume change of about 2% at a higher transformation Point at -147°C. The arrangement of sulphur atoms in the transient tetragonal form is determined from Patterson synthesis and trial and error method on the basis of the data given by electron diffraction. The structure is composed of double zigzag chains of sulphur atoms along the c -axis. The stable tetragonal structure of the lowest temperature phase is considered to be a super-structure of the intermediate form. The relations between these lattice transformations and changes of physical quantities are discussed.

The crystal structure of vanadium pentoxide

The crystal structure of vanadium pentoxide, V2O5, has been redetermined with three-dimensional data obtained by photographic and by counter methods, and has been refined by differential syntheses. The results are in closer agreement with those of Byström, Wilhelmi and Brotzen than with those of Ketelaar. The probable space group is Pmnm and the unit-cell dimensions are a = 11.510 Å, b = 4.369 Å, c = 3.563 Å. The structure is built up from distorted trigonal bipyramidal coordination polyhedra of O around V, which share edges to form zigzag double chains along [001] and are cross-linked along [100] through shared corners, thus forming sheets in the xz plane.