CVT法生长GaP多晶

阐述了CVT(化学气相输运)法生长GaP的基本反应和输运速度,采用CVT法生长出了GaP多晶.设计了石英管的结构以制造出一个局部的低温区域,防止了GaP在管壁的生长.生长出的GaP多晶相对密度为98;,红外透过率达到30;,努普硬度为611kg/mm2.散射颗粒测试表明主要的光散射颗粒为多晶中存在的孔隙.     

Gas-phase deprotonation of arylalkylamines. A collision-induced dissociation study

The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd.     

A new modification of an old framework: Hofmann layers with unusual tetracyanidometallate groups

Cyanidometallate complexes are highly versatile building units for the generation of functional porous materials. Here we report five new pillared Hofmann layer compounds incorporating the tetracyanidometallates [MoO(CN)(4)](2-) and [MnN(CN)(4)](2-). These metalloligands, which are new to this class of materials, have been combined with divalent 1st-row transition metals to produce Hofmann layers that are linked into three-dimensional frameworks by ditopic bridging dipyridyls. We report the structures and anomalous thermal expansion properties of five new materials: [Mn(H(2)O)(bpy)(?){MoO(CN)(4)(bpy)(?)}]·2H(2)O (1), [Mn(H(2)O)(bpy)(?){MnN(CN)(4)(bpy)(?)}]·2H(2)O (2), [Fe(H(2)O)(bpy)(?){MnN(CN)(4)(bpy)(?)}]·2H(2)O (3), [Co(H(2)O)(bpy)(?){MnN(CN)(4)(bpy)(?)}]·2H(2)O (4) and [{Mn(H(2)O)(2)}(?){Mn(bpa)(2)}(?){MoO(CN)(4)(bpa)(?)}]·MeOH (5), (where bpy = 4,4'-bipyridine and bpa = 4,4'-bipyridylacetylene).     

Structural diversity in coordination polymers constructed from a naphthalene-spaced dipyridyl ligand and iron(II) thiocyanate

Employing N,N??-bis-(4-pyridinylmethylene)-1,5-naphthalenediamine (nbpy4) and iron(II) thiocyanate as building blocks, three coordination polymers, [Fe(NCS)₂(nbpy4)(MeOH)₂] _n , 1, [Fe(NCS)₂(nbpy4)₂] _n ·2nCHCl₃·nH₂O·2nEtOH, 2, and [Fe(NCS)₂(nbpy4)(bpy)] _n ·2.5nDCM·0.75nH₂O, 3, have been prepared. The three metal?Corganic materials were prepared by varying the solvent systems used and the inclusion of a second pyridine containing ligand (4,4??-bipyridine, bpy). Single crystal X-ray diffraction revealed 1 to be a one-dimensional structure with hydrogen bonding between adjacent chains and 2?C3 to be two-dimension network solids with (4,4)-topologies.     

Structural and magnetic resolution of a two-step full spin-crossover transition in a dinuclear iron(II) pyridyl-bridged compound

A dinuclear iron(II) complex containing the new pyridyl bridging ligand, 2,5-di(2',2'-dipyridylamino)pyridine (ddpp) has been synthesised and characterised by single-crystal X-ray diffraction, magnetic susceptibility and M?ssbauer spectral methods. This compound, [Fe(2)(ddpp)(2)(NCS)(4)]4 CH(2)Cl(2), undergoes a two-step full spin crossover. Structural analysis at each of the three plateau temperatures has revealed a dinuclear molecule with spin states HS-HS, HS-LS and LS-LS (HS: high spin, LS: low spin) for the two iron(II) centres. This is the first time that resolution of the metal centres in a HS-LS ordered state has been achieved in a two-step dinuclear iron(II) spin-crossover compound. Thermogravimetric data show that the dichloromethane solvate molecules can be removed in two distinct steps at 120 degrees C and 200 degrees C. The partially de-solvated clathrate, [Fe(2)(ddpp)(2)(NCS)(4)]CH(2)Cl(2), undergoes a one-step transition with an increased transition temperature with respect to the as synthesised material. Structural characterisation of this material reveals subtle changes to the coordination geometries at each of the iron(II) centres and striking changes to the local environment of the dinuclear complex. The fully de-solvated material remains high spin over all temperatures. Interestingly, the solvent can be re-introduced into the monosolvated solid to achieve complete conversion back to the original two-step crossover material, [Fe(2)(ddpp)(2)(NCS)(4)]4 CH(2)Cl(2).     

Uniformities and Complemented Group Algebra Ideals

We continue an investigation of complementation in closed idealsof commutative group algebras. The main result here is a sufficientcondition for a closed ideal of a commutative group algebrato have a Banach space complement. This involves the comparisonof uniformities on the hull of the ideal.     

Isolation of NO(3)(-)-N as 1-phenylazo-2-naphthol (Sudan-1) for measurement of delta(15)N

The conversion of nitrate (NO(3)(-)) to 1-phenylazo-2-naphthol (Sudan-1) has been examined as a method for natural abundance measurement of delta(15)N of NO(3)(-). The reaction results in dilution of NO(3)(-)-N with only one reagent-derived N and the product is readily concentrated from dilute samples by reverse phase chromatography. There is systematic isotopic fractionation during the reaction, but this can be allowed for by analysing known NO(3)(-) standards along with each sample set. Sudan-1 prepared from surface water samples containing approximately 50 &mgr;g NO(3)(-)-N can be analysed by automated continuous flow isotope ratio mass spectrometry with a precision of 0.2 per thousand (one standard deviation) and the accuracy is not affected by interference from other nitrogenous species in the sample or reagents. Copyright 1999 John Wiley & Sons, Ltd.     

Dehydration of the nanoporous coordination framework ErIII[CoIII(CN)6].4(H2O): single crystal to single crystal transformation and negative thermal expansion in ErIII[CoIII(CN)6

Desorption of bound and unbound water molecules from the nanoporous coordination framework ErIII[CoIII(CN)6].4(H2O) to form the apohost, ErIII[CoIII(CN)6], proceeds via a single crystal to single crystal transformation in which the Er(III) cations change from 8- to 6-coordinate; dehydration results in a striking change in the thermal expansion properties.