Hydrothermal synthesis and characterization of 2D M(II)-Quinate (M = Co,Zn) metal-organic lattice assemblies: solid-state solution structure correlation in M(II)-hydroxycarboxylate systems

Co(II) and Zn(II) ions exhibit variable reactivity toward O-containing ligands in aqueous media, affording isolable materials with distinct solid-state lattice properties. d-(-)-quinic acid is a cellular α-hydroxycarboxylate metal ion binder, which reacts with Co(II) and Zn(II) under pH-specific hydrothermal conditions, leading to the isolation of two new species [Co(2)(C(7)H(11)O(6))(4)](n)·nH(2)O (1) and [Zn(3)(C(7)H(11)O(6))(6)](n)·nH(2)O (2). Compound 1 was characterized by elemental analysis, spectroscopic techniques (FT-IR, UV-visible, EPR), magnetic studies, and X-ray crystallography. Compound 2 was characterized by elemental analysis, spectroscopic techniques (FT-IR, ESI-MS), and X-ray crystallography. The 2D molecular lattices in 1 and 2 reveal the presence of octahedral M(II) units bound exclusively to quinate in a distinct fashion, thereby projecting a unique chemical reactivity in each investigated system. The magnetic susceptibility and solid-state/frozen solution EPR data on 1 support the presence of a high-spin octahedral Co(II) in an oxygen environment, having a ground state with an effective spin of S = 1/2. Concurrent aqueous speciation studies on the binary Zn(II)-quinate system unravel the nature and properties of species arising from Zn(II)-quinate interactions as a function of pH and molar ratio. The physicochemical profiles of 1 and 2, in the solid state and in solution, earmark the importance of (a) select synthetic hydrothermal reactivity conditions, affording new well-defined lattice dimensionality and nuclearity M(II)-quinate materials, (b) structural speciation approaches delineating solid state-aqueous solution correlations in the binary M(II)-quinate systems, and (c) pH-specific chemical reactivity in binary M(II)-quinate systems reflecting structurally unique associations of simple aqueous complexes into distinctly assembled 2D crystalline lattices.     

Low‐frequency scattering by a penetrable body with an eccentric soft or hard core

A plane wave is scattered by an acoustically soft or hard sphere, covered by a penetrable non‐concentric spherical lossless shell that disturbs the propagation of the incident wave field. The dimensions of the coated sphere are much smaller than the wavelength of the incident field. Low‐frequency theory reduces this scattering problem to a sequence of potential problems, which can be solved iteratively. Exactly one bispherical coordinate system exists that fits the given geometry of the obstacle. For the case of a soft and hard core, the exact low‐frequency coefficients of the zeroth and the first‐order for the near field as well as the first‐ and second‐order coefficients for the normalized scattering amplitude are obtained and the cross sections are calculated. Discussion of the results and their physical meaning is included. Copyright © 2009 John Wiley & Sons, Ltd.     

Coordination-driven self assembly of a brilliantly fluorescent rhomboid cavitand composed of bodipy-dye subunits

The two sp(3) hybridized fluorine atoms of a Bodipy dye have been synthetically replaced with the linear donor ligand 4-ethynylpyridine (-C≡C-Py) to form a rigid and highly symmetrical 109.5° building block in which the fluorophore subunit is vertically aligned to the plane formed by the -C≡C-Py donors. Upon reaction of the above tecton with a 90° organoplatinum acceptor unit, an intensely fluorescent rhomboid cavitand was manifested in solution. In contrast to the vast majority of coordination-driven self-assembled chromophoric systems, the present one fully conserves the excellent photophysical properties of the parent Bodipy dye. These unique features of the present metallosupramolecular entity constitute a fascinating metal-to-ligand self-assembled prototype for building compact and intensely luminescent materials with host-guest capabilities.     

A density version of the Halpern–Läuchli theorem

We prove a density version of the Halpern–Läuchli Theorem. This settles in the affirmative a conjecture of R. Laver.     

Fundamental Solutions of Linear Differential Equations in the Sense of Mnemofunctions

In this paper we discuss the definition and construction of the fundamental solution of a linear differential equation with constant coefficients in the algebra of mnemofunctions. This algebra contains the tempered distributions. We also present some examples including a physical illustration of our results for the equation u = .     

Controlled vinyl‐type polymerization of norbornene with a Nickel(II) diphosphinoamine/methylaluminoxane catalytic system

A novel nickel‐based complex coordinated with an asymmetric diphosphinoamine ligand was synthesized and fully characterized. Single crystals of good quality were also obtained, and the solid‐state structure of the complex was studied via X‐rays diffraction. The catalytic activity of this Ni(II) complex in the vinyl‐type polymerization of norbornene was studied with methylaluminoxane (MAO) as the cocatalyst/activator. The influence of the reaction time, the equivalents of MAO used, and the concentration of the monomer on: (i) the activity of the catalytic system; (ii) the isolated yield of the polymer; and (iii) the molecular weight and molecular weight distribution of the polymer were investigated. The isolated polynorbornene (PNB) yields are significantly higher compared with those reported for other similar nickel‐based systems. The as‐obtained PNBs are characterized by high molecular weights and relatively narrow and monomodal molecular weight distributions (amongst the narrowest reported in the literature). The linear dependence of the molecular weight of the obtained PNB on the concentration of norbornene points toward a controlled polymerization reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5241–5250, 2009     

The assessment of user-perceived web quality: Application of a satisfaction benchmarking approach

The assessment of website quality is considered as a problem of measuring user satisfaction, in order to analyse user perceptions and preferences. The presented pilot user satisfaction survey concerns the major cellular phone service providers in Greece. The analysis is based on a multicriteria preference disaggregation approach for satisfaction benchmarking analysis and consists of the following parts: (1) the user satisfaction analysis, which concerns the identification of customer preferences and includes the estimation of the relative importance and the demanding level of the different user satisfaction dimensions, and (2) the satisfaction benchmarking analysis, which is mainly focused on the performance evaluation of the competitive organisations against the satisfaction criteria, as well as the identification of the competitive advantages of each company. The results presented in this paper demonstrate how business organisations may locate their position against competition, pinpoint their weak points and determine which website characteristics will improve their global performance.     

A new method of glycosylation : anomeric hydroxyl activation by iminium salts

Starting from a free hemiacetalic hydroxyl group, the glycosylation is performed by means of the DMF-COCl₂ Vilsmeier-Haack reagent and silver tosylate. The nature of the reactive species is discussed.