A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.     

Justification of the Kirchhoff hypotheses and error estimation for two-dimensional models of anisotropic and inhomogeneous plates, including laminated plates

Asymptotic analysis of the problem describing deformation ofa thin cylindrical plate with clamped lateral side is performed.The problem is considered under the most general statement withthe plate being laminated and consisting of an arbitrary numberof nonhomogeneous and anisotropic (21 elastic moduli) layers.Explicit integral representations of the differential operatorswhich form the two-dimensional model of the plate are derived.In the case when the elastic moduli of each of the layers areconstant, these integral representations turn into algebraicones. The asymptotic procedure is justified with the help ofa weighted inequality of Korn's type. The error estimates obtainedgive a rigorous mathematical proof of both of Kirchhoff's hypotheses(kinematic and static) and shed light on the well-known intrinsicinconsistency of two of the hypotheses.     

ChemInform Abstract: Unique Seven-Node Rare-Earth Octacyanomolybdate(IV) Three-Dimensional Molecular Frameworks: {[Er(H2O)5(Er (H2O)4)3] [Mo(CN)8]3·11H2O}n and {[Eu(H2O)5(Eu (H2O)4)3] [Mo(CN)8]3·11H2O}n.

Good quality single crystals of the title compound are obtained by reaction of H₄[Mo(CN)₈] with the rare earth carbonates.     

Accurate crystal structures and chemical properties from NoSpherA2

The relationship between the structure and the properties of a drug or material is a key concept of chemistry. Knowledge of the three-dimensional structure is considered to be of such importance that almost every report of a new chemical compound is accompanied by an X-ray crystal structure – at least since the 1970s when diffraction equipment became widely available. Crystallographic software of that time was restricted to very limited computing power, and therefore drastic simplifications had to be made. It is these simplifications that make the determination of the correct structure, especially when it comes to hydrogen atoms, virtually impossible. We have devised a robust and fast system where modern chemical structure models replace the old assumptions, leading to correct structures from the model refinement against standard in-house diffraction data using no more than widely available software and desktop computing power. We call this system NoSpherA2 (Non-Spherical Atoms in Olex2). We explain the theoretical background of this technique and demonstrate the far-reaching effects that the improved structure quality that is now routinely available can have on the interpretation of chemical problems exemplified by five selected examples.

NoSpherA2 brings quantum crystallography to routine structure determination and to the analysis of chemical properties for any class of materials.     

Regioselectivity of reactions of vinyl- and isopropenylcyclopentadienide anions with electrophilic agents. Synthesis and crystal structures of complexes [C5H4C(Me)=CH2]ZrCl3 · 2THF and [C5Me4CH=CH2]ZrCl3 · 2THF

Regioselectivity of the reactions of lithium vinyl- and isopropenylcyclopentadienides C₅H₄C(R)=CH₂ ^-Li⁺(R = H, Me) and lithium tetramethylvinylcyclopentadienide C₅Me₄CH=CH₂ ^-Li⁺ with various electrophilic agents (Me₃SiCl, Me₃SnCl, Et₂PCl, 2-chloro-1, 3-dioxaphospholane, and MeI) was studied. Two new monocyclopentadienyl zirconium complexes, [C₅H₄C(Me) = CH₂]ZrCl₃ · 2THF and [C₅Me₄CH=CH₂]ZrCl₃ · 2THF, were synthesized. Their crystal structures were established by X-ray diffraction. The results of quantum chemical calculations for the C₅H₄C(R) = CH₂ ^- (R = H, Me) and C₅Me₄CH=CH₂ ^- anions by the DFT method (RMPW1PW91) with the 6-311+G(d, p) split valence basis set are in good agreement with experimental data on the regioselectivity of their reactions with electrophilic agents.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 390–399, February, 2005.     

A novel synthetic strategy for hexanuclear supramolecular architectures

Hexanuclear cage complexes [M6L6X](X)5 [M = Cu(I), Ag(I); L = 6,6'-bis(4-ethynylpyridine)2,2'-bipyridine; X = BF4-, SbF6-] have been prepared using a self-assembly approach; these architectures encapsulate anions in the solid-state and are fluxional in solution.     

A design strategy for four-connected coordination frameworks

Reactions of tetrahedral Cu(I) and Ag(I) cations with 2,3,4,5-tetra(4-pyridyl)thiophene allows targeted construction of coordination frameworks with zeolite-like, 4(2).8(4), topologies.