Preparation, structures, and electrochemistry of a new polyoxometalate-based organic/inorganic film on carbon surfaces

The preparation, structure, and electrochemical and electrocatalytical properties of a new polyoxometalate-based organic/inorganic film, composed of cetyl pyridinum 11-molybdovanadoarsenate (CPMVA) molecules, have been studied. Cyclic potential scanning in acetone solution led to a stable CPMVA film formed on a highly oriented pyrolytic graphite (HOPG) surface. X-ray photoelectron spectroscopy, scanning tunneling microscopy, and cyclic voltammetry were used for characterizing the structure and properties of the CPMVA film. These studies indicated that self-aggregated clusters were formed on a freshly cleaved HOPG surface, while a self-organized monolayer was formed on the precathodized HOPG electrode. The CPMVA film exhibited reversible redox kinetics both in acidic aqueous and in acetone solution, which showed that it could be used as a catalyst even in organic phase. The CPMVA film remained stable even at pH > 7.0, and the pH dependence of the film was much smaller than that of its inorganic film (H4AsMo11VO40) in aqueous solution. The CPMVA film showed strong electrocatalysis on the reduction of bromate, and the catalytic currents were proportional to the square of the concentration of bromate. The new kind of polyoxometalate with good stability may have extensive promise in catalysis.

X-ray crystal structure and molecular mechanics calculations of (2,6-iso-dipropyl-phenylamide) dimethyl (tetra-methylcyclopenta-dienyl) silane titanium dichloride

Crystal and molecular structure of (2.6-dipropylphenylamide) dimethyl (tetra-methyl cyclopentadienyl) silane titanium dichloride (I) was fully characterized by X-ray diffraction. The crystal is obtained from a mixture of ether/hexane as orthorhombic. with a = 12.658 (3) Angstrom. b = 16.62 (3) Angstrom. c = 11.760 (2) Angstrom. V = 2474.2 (9) Angstrom(3). Z = 4, space group Pnma. R = 0.0399; Componud I compose of the pi-bounded ring with its dimethylsilyl-dipropyl phenyl amido group and the two terminal chloride atoms coordinated to central metal to form a so-called constrained geometry catalyst (CGC) structure. The result of molecular mechanics (MM) calculations on compound I shows that bond lengths and bond angles from the MM calculation are comparable to the data obtained from the X-ray diffraction study. The relation of the structure of CGCs and their catalytic activity by MM calculations is also discussed.

Study on new typical ionic clusters K+ (KNO3)(n) and NO3-(KNO3)(m)

The sample solution of KNO3 is ejected into the gas phase and the ionic dusters of K+(KNO3)(n) and NO3-(KNO3)(m) we formed and observed by electrospray ionization mass spectrometry (ESIMS). The full mass spectra of both the positive ion and the negative ion show that the differences between each peak nearby are all about 101(m/z), which correspond to the molecular weight of KNO3. The general formula of the ionic clusters can be assigned as K+ (KNO3)(n) and NO3--(KNO3)(m).

Ultrathin multilayer films incorporating Keggin-type heteropolyanion clusters

Two new ultrathin multiplayer films have been successfully prepared fi-om Keggin-type heteropoly acids H-4[SiW12O40] and H-3[PMo12O40] with polyelectrolytes PEI, PSS, and PAH, using the electrostatic layer-by-layer self-assembly, technique. The XR results reveal their film thickness at nanoscale (similar to 20 nm). According to the AFM images, it is believed that the surface roughness (rough degree of film surface) of the polyelectrolyte-polyoxometalate film greatly depends on the kind of polyoxometalates.

Hydrothermal synthesis and structure of [{Mo8V4O36(VO4)(VO)(2)}(n)](7n-) bi-capped alpha-Keggin fragments linked to a chain

The title compound, (H(2)en)(3)H3O {MO8V4O36 (VO4) (VO)(2)} . 4H(2)O, was hydrothermally synthesized and structurally characterized by means of IR, ESR spectrum and single crystal X-ray diffraction. It crystallized in a monoclinic system with space group P2(1)/c, a=1. 980 4(4) nm, b=2. 063 4(4) nm, c=1. 192 0(2) nm, (beta =94. 76(3)degrees and deep black colour. The compound contains V-centered bi-capped alpha -Keggin fragments {Mo8V7O42} that are linked together by edge-shared units (VO5)-O-N via V-O-V bonds, forming a chain.

Hydrothermal synthesis and crystal structure of [{Cu(2,2 '-bpy)(2)}(2)Mo8O26]: a beta-octamolybdate cluster covalently bonded to two {Cu(2,2 '-bpy)(2)}(2+) coordination complexes via bridging oxo groups

An organic-inorganic hybrid solid, (Cu(2,2'-bpy)(2))(2)Mo8O26, has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Dark green crystals crystallize in the orthorhombic system, space group Pna21, a = 24.164(5), b = 18.281(4), c = 11.877(2) Angstrom, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, V= 5247(2) Angstrom (3), Z = 4, lambda (MoK alpha) = 0.71073 Angstrom (R(F) = 0.0331 for 5353 reflections). Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range 1.69 degrees < theta < 25.04 degrees using the omega -scan technique. The structure was solved by the direct method and refined by full-matrix least squares on F-2 using SHELXL-93. The structure of this compound consists of discrete (Cu(2,2'-bpy)(2))(2)Mo8O26 clusters, constructed from beta -octamolybdate subunits ((Mo8O26)(4-)) covalently bonded to two (Cu(2,2'-bpy)(2))(2+) coordination complexes via bridging oxo groups that connect two adjacent molybdenum sites. (C) 2001 Academic Press.

Hydrothermal synthesis and structure of a bi-capped Keggin polyoxoanion, [(As2AsMo8V4O40)-As-III-Mo-V-O-IV](5-)

The title compound, [NH3CH2CH2CH2NH2][NH3CH2CH2CH2NH3](2)[As-2(III) As-v Mo-8 V-4(IV) O-40] (.) 5H(2)O, was hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Crystal data: monoclinic, C2/c, a = 45.375(9) Angstrom, b = 11.774(2) Angstrom, c = 23.438(5) Angstrom, beta = 96.62(3)degrees. X-ray crystallographic study showed that the crystal structure was constructed by bi-capped alpha -Keggin fragments [(As2AsMo8V4O40)-As-III-Mo-v-O-IV](5-) polyoxoanion. (C) 2001 Elsevier Science B.V. All rights reserved.

Local similarity in organic crystals and the non-uniqueness of X-ray powder patterns

Two new concepts for molecular solids, 'local similarity' and 'boundary-preserving isometry', are defined mathematically and a theorem which relates these concepts is formulated. 'Locally similar' solids possess an identical short-range structure and a 'boundary-preserving isometry' is a new mathematical operation on a finite region of a solid that transforms mathematically a given solid to a locally similar one. It is shown further that the existence of such a 'boundary-preserving isometry' in a given solid has infinitely many 'locally similar' solids as a consequence. Chemical implications, referring to the similarity of X-ray powder patterns and patent registration, are discussed as well. These theoretical concepts, which are first introduced in a schematic manner, are proved to exist in nature by the elucidation of the crystal structure of some diketopyrrolopyrrole (DPP) derivatives with surprisingly similar powder patterns. Although the available powder patterns were not indexable, the underlying crystals could be elucidated by using the new technique of ab initio prediction of possible polymorphs and a subsequent Rietveld refinement. Further ab initio packing calculations on other molecules reveal that 'local crystal similarity' is not restricted to DPP derivatives and should also be exhibited by other molecules such as quinacridones. The 'boundary-preserving isometry' is presented as a predictive tool for crystal engineering purposes and attempts to detect it in crystals of the Cambridge Structural Database (CSD) are reported.

X-ray photoelectron spectroscopy and mass spectrum of organic tin compounds

The relationship between the chemical displacement of the binding energy and the different chemical environment for 12 organic tin compounds was studied by means of X-ray photoelectron spectronscopy. The different substituents in the compounds have influence on the tin outer electron and Sn-O bond, which was discussed by Xray photoelectron spectroscopy and mass spectrum.

Hydrothermal synthesis and crystal structure of Co(En)(3)MoO4

Co(En)(3)MoO4 was synthesized by using the method of hydrothermal synthesis and characterized by elemental analysis, IR, ESR and single-crystal X-ray methods. It crystallizes in hexagonal space group P (3) over bar C1 with a=1.596 4(2) nm, b=1.596 4(2) nm, c = 0.993 5(2) nm, alpha=beta=90 degrees gamma=120 degrees, M-c=399.18, V=2.192 6(6) nm(3), D-c=1.814 g/nm(3), Z=6, F(000)=1 2181 R-1=0.070 3, R-w=0.220 7. According to separation of anion which acted on electrostatic potential, the anion and cation ions formed a type of organic and inorganic material.

Synthesis and crystal structure of a novel butterfly-like complex, [WOS3Cu2(PPh3)(2)(Py)(2)] (Py = pyridine)

A new butterfly-like cluster [WOS3Cu2(PPh3)(2)(Py)(2)] was obtained by reacting [WOS3Cu2(PPb3)(3)] with pyridine. The crystal structure of the cluster has been determined by X-ray diffraction. The compound shows an unusual folded structure, in which two 4-coordinate Cu atoms are bound to the WOS3 moiety via two S-S edges.

The NMR-spectroscopic and X-ray crystal-structural characterization of two Cp*Ir halfsandwich complexes containing the 1,2-dicarba-closo-dodecaborane-1,2-diselenolato ligand

The reaction of [Cp*IrCl2](2) with dilithium 1,2-orthocarborane-1,2-diselenolate 3 leads to the green 16-electron diselenolene complex [Cp*Ir{Se2C2(B10H10)}] (4) which takes up two-electron ligands such as trimethylphosphane to give the 18-electron diselenolate derivative [Cp*Ir(PMe3)-{Se2C2(B10H10)}] (5). The molecular structures of 4 and 5 were determined by X-ray crystal structure analysis. The Se-77-nuclear shielding in 4 is lower by almost 500 ppm relative to that in 5.

X-ray photoelectron spectroscopy and mass spectra study of alpha-amino acid

X-ray photoelectron spectroscopy and mass spectrometry have been used to study the ten alpha-Amino Acids. The chemical shiftss of N-1s electron binding energy have been explained by means of the difference in the hydrocarbon group of amino acids. The influence of the hydrocarbon group on NH2 has been disscussed using the XPS and MS results.

Synthesis and x-ray structure of a highly symmetrical selenium-centered hexanuclear neodymium complex, [(Cp6Nd6Se13)-Nd-t](-) (Cp-t=eta(5)-(BuC5H4)-C-t)

The half-sandwich tert-buthylcyclopentadienyl neodymium complex [(CpNdCl2)-Nd-t(THF)(2)](2) (1) reacts with Na2Se5 to give organoneodymium polyselenide complex [Na(THF)(6)][(Cp6Nd6)-Nd-t(mu(6)-Se)(mu(2)-Se-2)(6)] (2) which has been characterized by X-ray crystallography.

A ferric molybdenum phosphate with a tunnel: hydrothermal synthesis and structure of (NH3CH2CH2NH3)(2)center dot(NH3CH2CH2NH2)(3)center dot Na center dot[Fe2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 7H(2)O

A new ferric molybdenum phosphate containing a tunnel structure and crystallographically different clusters has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. A probe reaction of the oxidation of acetaldehyde with H2O2 using the tide compound as catalyst was carried out in a liquid-solid system, showing that the title compound had high catalytic activity in the reaction. (C) 1998 Elsevier Science S.A. All rights reserved.