Trigonal Prism (trigonal + prism)

Distribution by Scientific Domains


Selected Abstracts


ChemInform Abstract: La8Br7Ni4: Ribbons of Ni Hexagons in Condensed La6 Trigonal Prisms.

CHEMINFORM, Issue 10 2009
Chong Zheng
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


La4Br2Al5 and Ce4Br2Ga5: Three-Dimensional Metal Networks Embedded in Condensed Ln6 Trigonal Prisms.

CHEMINFORM, Issue 12 2004
Chong Zheng
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Gd3Pt4In12 and Tb3Pt4In12 , New Ternary Indides with Condensed Distorted [PtIn6] Trigonal Prisms.

CHEMINFORM, Issue 50 2002
Ute Ch.
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Structure Comparison of Early and Late Lanthanide(III) Homodinuclear Macrocyclic Complexes with the Polyamine Polycarboxylic Ligand H8OHEC

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2004
Ulrike A. Böttger
Abstract The solid-state structures of two new homodinuclear chelate complexes with the late lanthanide(III) ions Yb and Lu, [Na2(Yb2OHEC)].14.5H2O (1), and [Na2(Lu2OHEC)].14.5H2O (2) (H8OHEC = 1,4,7,10,14,17,20,23-octaazacyclohexacosane- 1,4,7,10,14,17,20,23-octaacetic acid), have been determined by X-ray crystal structure analysis. Each lanthanide(III) ion is coordinated by eight donor atoms of the ligand and the geometry of the coordination polyhedron approaches a bicapped trigonal prism. These structures are compared with those of the homodinuclear chelate complexes with the same ligand and the mid to early lanthanide(III) ions Gd, Eu, La and also Y. A distinctive structural change occurs across the lanthanide series. The centrosymmetric mid to early lanthanide(III) complexes are all ninefold-coordinated in a capped square antiprismatic arrangement with a water molecule coordinated in a prismatic position. This structure is maintained in aqueous solution, together with an asymmetric minor isomer. The late lanthanide(III) OHEC complexes not only lack the inner-sphere water, but the change of coordination sphere also results in a loss of symmetry of the whole complex molecule. The observed change of coordination mode and number of the lanthanide ion may offer a geometric model for the isomerization process in eight- and ninefold-coordinated complex species that are isomers in a possible coordination equilibrium observed by NMR in aqueous solution. This model may also explain the intramolecular rearrangements necessary during water exchange in the inner coordination sphere of the complex [(Gd2OHEC)(H2O)2]2, through a slow dissociative mechanism. Protonation constants of the H8OHEC ligand and complex formation constants of this ligand with GdIII, CaII, CuII and ZnII have been determined by solution thermodynamic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


Synthesis and Microstructural Characterisation of Two New One-Dimensional Members of the (A3NiMnO6),(A3Mn3O9), Homologous Series (A = Ba, Sr)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2003
María Hernando
Abstract Two new members of the one-dimensional (A3NiMnO6),(A3Mn3O9), homologous series, with the compositions (Sr0.75Ba0.25)5NiMn3O12 and Sr9Ni2Mn5O21, have been synthesised. Their structures can each be described as a hexagonal array of infinite one-dimensional chains of face-sharing polyhedra, running parallel to the c axis and separated by the Sr/Ba cations. The structure of (Sr0.75Ba0.25)5NiMn3O12, which constitutes the (, = 3, , = 2) member of the series, is made up of three face-sharing octahedra linked by one trigonal prism. For Sr9Ni2Mn5O21 (, = 2, , = 1) the sequence of polyhedra along the chains corresponds to a motif consisting of two octahedra,one trigonal prism,three octahedra,one trigonal prism. The manganese atoms occupy the octahedral sites in both phases, while the Ni2+ cations are distributed in the trigonal-prismatic sites in a disordered way. Only a small fraction of these (close to 20%) is located at the centres of the trigonal prisms, 80% being displaced towards the rectangular faces of the polyhedra and giving rise to a square-planar-like coordination. Both oxides present twinned microstructures, as evidenced by SAED and HREM. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]


Mo4(,3 -allyl)4Cl2(OH)2(CO)8: the first cubane-type Mo2+ organometallic complex with ,3 -OH and ,3 -Cl bridges

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009
Tatiana R. Amarante
The reaction between fluorenyllithium and Mo(,3 -C3H5)Cl(NCMe)2(CO)2 led to the isolation of di-,3 -chlorido-di-,3 -hydroxido-tetrakis[(,3 -allyl)dicarbonylmolybdenum(II)],9-fluorenone,tetrahydrofuran (1/1/1), [Mo4(C3H5)4Cl2(OH)2(CO)8]·C4H8O·C13H8O. The tetrametallic Mo4 unit constitutes the first example of a complex containing simultaneously two ,3 -OH groups and two ,3 -Cl anions capping the metallic trigonal prism. The four crystallographically independent Mo2+ centres exhibit distorted octahedral geometry with the ,3 -allyl groups being trans -coordinated to a ,3 -OH group and the carbonyl groups occupying the equatorial plane. Space-filling tetrahydrofuran and 9-fluorenone molecules are engaged in strong O,H...O hydrogen-bonding interactions with Mo4(,3 -allyl)4Cl2(OH)2(CO)8 complexes. [source]


K2[O(HgSO3)3], a new sulfitomercurate with an [OHg3] core

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2008
Matthias Weil
The structure of dipotassium ,3 -oxido-tris[sulfitomercurate(II)], K2[O(HgSO3)3], is characterized by segregation of the K+ cations and complex [O(HgSO3)3]2, anions into layers parallel to (010). The anion has m symmetry and is a new example of a ,3 -oxido-trimercurate complex with a central [OHg3] core. This unit adopts the shape of a flat, almost trigonal, pyramid (mean O,Hg = 2.072,Å and mean Hg,O,Hg = 110.8°). The two independent Hg,S bonds have nearly the same length (mean Hg,S = 2.335,Å). Due to intermolecular O...Hg donor,acceptor interactions greater than 2.65,Å, the O,Hg,S fragments are slightly bent. The [KO9] coordination polyhedron of the K+ cation approaches a distorted tricapped trigonal prism with a [6+1+2] coordination. [source]


Tetrastrontium dimanganese copper nonaoxide, Sr4Mn2CuO9

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2002
Ahmed El Abed
Single crystals of Sr4Mn2.09Cu0.91O9 have been grown by flux synthesis and the structure, closely related to the hexagonal perovskite 2H, was solved from single-crystal X-ray data in space group P321. The structure of Sr4Mn2CuO9 is composed of chains of face-sharing polyhedra with a sequence of two octahedra and one trigonal prism. The octahedra are filled by Mn atoms and the Cu atoms are randomly distributed at the centres of the square faces of the trigonal prism. A stacking fault is observed within one of the two chains, which can be attributed to a shifting of the chain along the c axis. [source]


Designing Simple Tridentate Ligands for Highly Luminescent Europium Complexes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 41 2009

Abstract A series of tridentate benzimidazole-substituted pyridine-2-carboxylic acids have been prepared with a halogen, methyl or alkoxy group in the 6-position of the benzimidazole ring, which additionally contains a solubilising N -alkyl chain. The ligands form neutral homoleptic nine-coordinate lanthanum, europium and terbium complexes as established from X-ray crystallographic analysis of eight structures. The coordination polyhedron around the lanthanide ion is close to a tricapped trigonal prism with ligands arranged in an up,up,down fashion. The coordinated ligands serve as light-harvesting chromophores in the complexes with absorption maxima in the range 321,341,nm (,=(4.9,6.0)×104,M,1,cm,1) and triplet-state energies between 21,300 and 18,800,cm,1; the largest redshifts occur for bromine and electron-donor alkoxy substituents. The ligands efficiently sensitise europium luminescence with overall quantum yields () and observed lifetimes (,obs) reaching 71,% and 3.00,ms, respectively, in the solid state and 52,% and 2.81,ms, respectively, in CH2Cl2 at room temperature. The radiative lifetimes of the Eu(5D0) level amount to ,rad=3.6,4.6,ms and the sensitisation efficiency ,sens=(,rad/,obs) is close to unity for most of the complexes in the solid state and equal to approximately 80,% in solution. The photophysical parameters of the complexes correlate with the triplet energy of the ligands, which in turn is determined by the nature of the benzimidazole substituent. Facile modification of the ligands makes them promising for the development of brightly emissive europium-containing materials. [source]


Polyhedral Structures with Three-, Four-, and Five Fold Symmetry in Metal-Centered Ten-Vertex Germanium Clusters

CHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2008
Bruce King Prof.
Abstract Studies using density functional theory (DFT) at the hybrid B3LYP level indicate that the relative energies of structures with three-fold, four-fold, and five-fold symmetry for centered 10-vertex bare germanium clusters of the general type M@Ge10z depend on the central metal atom M and the skeletal electron count. For M@Ge10 clusters with 20 skeletal electrons the DFT results agree with experimental data on the isoelectronic centered 10-vertex bare metal clusters. Thus the lowest energy structure for Ni@Ge10, isoelectronic with the known Ni@In1010,, is a C3v polyhedron derived from the tetracapped trigonal prism. However, Zn@Ge102+ is isoelectronic with the known cluster Zn@In108,, which has the lowest energy structure, a D4d bicapped square antiprism. For the clusters Ni@Ge102,, Cu@Ge10,, and Zn@Ge10 that have 22 skeletal electrons the lowest energy structures are the D4d bicapped square antiprism predicted by the Wade,Mingos rules. For the clusters Ni@Ge104,, Cu@Ge103,, and Zn@Ge102, that have 24 skeletal electrons the lowest energy structures are C3v polyhedra with 10 triangular faces and 3 quadrilateral faces derived from a tetracapped trigonal prism by extreme lengthening of the edges of the capped triangular face of the underlying trigonal prism. For the clusters Cu@Ge105, and Zn@Ge104, that have 26 skeletal electrons the lowest energy structures are the D5d pentagonal antiprisms predicted by the Wade,Mingos rules and the C3v tetracapped trigonal prism as a somewhat higher energy structure. However, for the isoelectronic Ni@Ge106, the relative energies of these two structure types are reversed so that the C3v tetracapped trigonal prism becomes the global minimum. The effects of electron count on the geometries of the D5d pentagonal prism and D4d bicapped square antiprism centered metal cluster structures are consistent with the bonding/antibonding characteristics of the corresponding HOMO and LUMO frontier molecular orbitals. [source]


Hydration of Lanthanoid(III) Ions in Aqueous Solution and Crystalline Hydrates Studied by EXAFS Spectroscopy and Crystallography: The Myth of the "Gadolinium Break"

CHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2008
Ingmar Persson Prof.
Abstract The structures of the hydrated lanthanoid(III) ions including lanthanum(III) have been characterized in aqueous solution and in the solid trifluoromethanesulfonate salts by extended X-ray absorption fine structure (EXAFS) spectroscopy. At ambient temperature the water oxygen atoms appear as a tricapped trigonal prism around the lanthanoid(III) ions in the solid nonaaqualanthanoid(III) trifluoromethanesulfonates. Water deficiency in the capping positions for the smallest ions starts at Ho and increases with increasing atomic number in the [Ln(H2O)9,x](CF3SO3)3 compounds with x=0.8 at Lu. The crystal structures of [Ho(H2O)8.91](CF3SO3)3 and [Lu(H2O)8.2](CF3SO3)3 were re-determined by X-ray crystallography at room temperature, and the latter also at 100,K after a phase-transition at about 190,K. The very similar Ln K- and L3 -edge EXAFS spectra of each solid compound and its aqueous solution indicate indistinguishable structures of the hydrated lanthanoid(III) ions in aqueous solution and in the hydrated trifluoromethanesulfonate salt. The mean LnO bond lengths obtained from the EXAFS spectra for the largest ions, La,Nd, agree with estimates from the tabulated ionic radii for ninefold coordination but become shorter than expected starting at samarium. The deviation increases gradually with increasing atomic number, reaches the mean LnO bond length expected for eightfold coordination at Ho, and increases further for the smallest lanthanoid(III) ions, Er,Lu, which have an increasing water deficit. The low-temperature crystal structure of [Lu(H2O)8.2](CF3SO3)3 shows one strongly bound capping water molecule (LuO 2.395(4),Å) and two more distant capping sites corresponding to LuO at 2.56(1),Å, with occupancy factors of 0.58(1) and 0.59(1). There is no indication of a sudden change in hydration number, as proposed in the "gadolinium break" hypothesis. [source]


Synthesis and Microstructural Characterisation of Two New One-Dimensional Members of the (A3NiMnO6),(A3Mn3O9), Homologous Series (A = Ba, Sr)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2003
María Hernando
Abstract Two new members of the one-dimensional (A3NiMnO6),(A3Mn3O9), homologous series, with the compositions (Sr0.75Ba0.25)5NiMn3O12 and Sr9Ni2Mn5O21, have been synthesised. Their structures can each be described as a hexagonal array of infinite one-dimensional chains of face-sharing polyhedra, running parallel to the c axis and separated by the Sr/Ba cations. The structure of (Sr0.75Ba0.25)5NiMn3O12, which constitutes the (, = 3, , = 2) member of the series, is made up of three face-sharing octahedra linked by one trigonal prism. For Sr9Ni2Mn5O21 (, = 2, , = 1) the sequence of polyhedra along the chains corresponds to a motif consisting of two octahedra,one trigonal prism,three octahedra,one trigonal prism. The manganese atoms occupy the octahedral sites in both phases, while the Ni2+ cations are distributed in the trigonal-prismatic sites in a disordered way. Only a small fraction of these (close to 20%) is located at the centres of the trigonal prisms, 80% being displaced towards the rectangular faces of the polyhedra and giving rise to a square-planar-like coordination. Both oxides present twinned microstructures, as evidenced by SAED and HREM. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]


Reciprocal-space mapping of epitaxic thin films with crystallite size and shape polydispersity

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2006
A. Boulle
A development is presented that allows the simulation of reciprocal-space maps (RSMs) of epitaxic thin films exhibiting fluctuations in the size and shape of the crystalline domains over which diffraction is coherent (crystallites). Three different crystallite shapes are studied, namely parallelepipeds, trigonal prisms and hexagonal prisms. For each shape, two cases are considered. Firstly, the overall size is allowed to vary but with a fixed thickness/width ratio. Secondly, the thickness and width are allowed to vary independently. The calculations are performed assuming three different size probability density functions: the normal distribution, the lognormal distribution and a general histogram distribution. In all cases considered, the computation of the RSM only requires a two-dimensional Fourier integral and the integrand has a simple analytical expression, i.e. there is no significant increase in computing times by taking size and shape fluctuations into account. The approach presented is compatible with most lattice disorder models (dislocations, inclusions, mosaicity, ,) and allows a straightforward account of the instrumental resolution. The applicability of the model is illustrated with the case of an yttria-stabilized zirconia film grown on sapphire. [source]


K3TaF8 from laboratory X-ray powder data

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010
ubomír Smr
The crystal structure of tripotassium octafluoridotantalate, K3TaF8, determined from laboratory powder diffraction data by the simulated annealing method and refined by total energy minimization in the solid state, is built from discrete potassium cations, fluoride anions and monocapped trigonal,prismatic [TaF7]2, ions. All six atoms in the asymmetric unit are in special positions of the P63mc space group: the Ta and one F atom in the 2b (3m) sites, the K and two F atoms in the 6c (m) sites, and one F atom in the 2a (3m) site. The structure consists of face-sharing K6 octahedra with a fluoride anion at the center of each octahedron, forming chains of composition [FK3]2+ running along [001] with isolated [TaF7]2, trigonal prisms in between. The structure of the title compound is different from the reported structure of Na3TaF8 and represents a new structure type. [source]


Tb2Ni2Mg3: a new structure type derived from the Ru3Al2B2 type

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2007
Pavlo Solokha
Single crystals of diterbium dinickel trimagnesium, Tb2Ni2Mg3, were synthesized from the elements by induction melting. The novel compound crystallizes in the space group Cmmm with one Mg atom of site symmetry mmm and the Tb, Ni and other Mg atom in m2m positions. This ternary compound represents a new structure type that is derived from Ru3Al2B2 by way of Wyckoff site distribution. The two-layer structure of Tb2Ni2Mg3 is a new representative of a homologous linear structure series of general formula R,k+nX2nR,,2m+k based on structural fragments of the ,-Fe, CsCl and AlB2 structure types. The Tb atoms in the structure are enclosed in 17-vertex polyhedra, while rhombododeca­hedra and distorted rhombododeca­hedra surround the Mg atoms, and equatorially tricapped trigonal prisms form around the Ni atoms. All inter­atomic distances indicate metallic type bonding. [source]


Redetermination of the lanthanum iron sulfide La52Fe12S90

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2006
Allison M. Mills
A redetermination of the structure of `La32.66Fe11S60' in the trigonal space group Rm led to the new formula La52Fe12S90 and to a redefinition of the structure type. In the structure, the Fe2+ cations occur in Fe2S9 dimers of face-sharing octa­hedra (with 3m symmetry). The dimers are linked by face- and vertex-sharing bi- and tricapped LaS6 trigonal prisms (with m symmetry) to form a three-dimensional network containing two types of cubocta­hedral cavities. The larger cavities remain empty, while the smaller ones accommodate alternative sites for disordered La3+ cations. [source]


Cerium iron sulfide, Ce3Fe1.94S7

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2004
Allison M. Mills
Tricerium(III) diiron(II,III) hepta­sulfide, Ce3Fe1.94S7, crystallizes in the polar hexagonal space group P63 and adopts the Ce6Al3.33S14 structure type. The Fe atoms occupy both tetrahedral and octahedral sites. Isolated FeS4 tetrahedra, all pointing in the same direction, are stacked along the threefold rotation axes. Chains of face-sharing FeS6 octahedra propagate along the 63 axis. Vacancies resulting from the partial oxidation of Fe2+ to Fe3+ occur exclusively in the octahedral Fe sites. The Ce atoms are coordinated by [7+1] S atoms, which form bicapped trigonal prisms. [source]


Ca4IrO6, Ca3MgIrO6 and Ca3ZnIrO6

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2001
Matthew J. Davis
Single crystals of tetracalcium iridium hexaoxide, Ca4IrO6, tricalcium magnesium iridium hexaoxide, Ca3MgIrO6, and tricalcium zinc iridium hexaoxide, Ca3ZnIrO6, were prepared via high-temperature flux growth and structurally characterized by single-crystal X-ray diffraction. The three compounds are isostructural and adopt the K4CdCl6 structure type, comprised of chains of alternating face-shared [CaO6], [MgO6] or [ZnO6] trigonal prisms and [IrO6] octahedra, surrounded by columns of Ca2+ ions. [source]