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Hexagonal Channels (hexagonal + channel)

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Chemistry100%

Selected Abstracts

Crystal Structure and Properties of Strontium Phosphate Apatite with Oxocuprate Ions in Hexagonal Channels.

CHEMINFORM, Issue 20 2003
Pavel E. Kazin
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Hybrid Magnetic Materials Based on Nitroxide Free Radicals and Extended Oxalato-Bridged Bimetallic Networks

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2005
Antonio Alberola
Abstract A series of hybrid organic-inorganic magnets of formula p -rad[MIICr(ox)3] [M = Mn (1), Co (2), Ni (3), Zn (4)] and m -rad[MIICr(ox)3] [M = Mn (5), Co (6)], in which N -methylpyridinium cations bearing a nitronyl nitroxide moiety in positions 3 (m -rad) or 4 (p -rad) of the pyridine ring coexist with the 2D honeycomb-like oxalato-bridged bimetallic lattice, has been prepared and studied by AC and DC magnetic susceptibility measurements and EPR spectroscopy. In general, the physical properties of these magnets are not altered significantly by the insertion of the nitronyl nitroxide radicals although these paramagnetic molecules seem to interact weakly with the inorganic network as demonstrated by EPR spectroscopy. Some differences can also be observed between the p -rad and m -rad series, i.e. m -rad derivatives have smaller values for the critical temperatures and coercive fields. We also report on the X-ray crystal structures and magnetic properties of p -rad[Mn(H2O)Cr(ox)3]·2H2O (7) and m -rad[Mn(H2O)2Cr(ox)3]·2H2O (8), two extended oxalato-bridged compounds with new topologies. Compound 7 is antiferromagnetic and its structure is a 3D achiral lattice in which zigzag ferromagnetic MnCr chains (J/k = +0.8 K) are interconnected to form hellicoidal hexagonal channels with the cationic free radicals residing in the free space. Compound 8, however, exhibits a ladder-like structural pattern with competing magnetic interactions and paramagnetic behaviour down to low temperatures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

The triple pyrophosphate Cs3CaFe(P2O7)2

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010
Nataliya Yu.
The complex phosphate tricaesium calcium iron bis(diphosphate), Cs3CaFe(P2O7)2, has been prepared by the flux method. Isolated [FeO5] and [CaO6] polyhedra are linked by two types of P2O7 groups into a three-dimensional framework. The latter is penetrated by hexagonal channels along the a axis where three Cs atoms are located. Calculations of caesium Voronoi,Dirichlet polyhedra give coordination schemes for the three Cs atoms as [8,+,3], [9,+,1] and [9,+,4]. The structure includes features of both two- and three-dimensional frameworks of caesium double pyrophosphates. [source]

Photovoltaic activity of Ti/MCM-41

CHEMPHYSCHEM, Issue 1 2009
Pedro Atienzar Dr.
Abstract Ti/MCM-41 is a well-known heterogeneous catalyst for alkene epoxidation with organic peroxides. This titanosilicate contains isolated titanium atoms forming part of a framework of mesoporous silica whose structure is formed by parallel hexagonal channels 3.2 nm in diameter. The surface area and porosity of Ti/MCM-41 are about 880 m2,g,1 and 0.70 cm3,g,1, respectively. These values are among the highest for any material. Herein, we show that Ti/MCM-41 exhibits photovoltaic activity. Dye-sensitized solar cells using mesoporous Ti/MCM-41 (2.8,5.7,% Ti content) as active layer, black dye N3 as photosensitizer and I3,/I, in methoxyacetonitrile as electrolyte exhibit a VOC, JSC and FF of 0.44 V, 0.045 mA,cm,2 and 0.33, respectively. These values compare well against 0.75 V, 4.1 mA,cm,2 and 0.64, respectively, measured for analogous solar cells using conventional P-25 TiO2. However, the specific current density (JSC/Ti atom) for the Ti/MCM-41 is very similar to that of P25 TiO2. [source]