A family of double-bowl pseudo metallocalix[6]arene discs

We report the synthesis and magnetic characterisation of a series of planar [M?] (M= Ni(II), Zn(II)) disc complexes [Ni?(OH)?(L?)?](NO?)? (1), [Ni?(OH)?(L?)?](NO?)?·2MeOH (2), [Ni?(OH)?(L?)?](NO?)?·3MeNO? (3), [Ni?(OH)?(L?)?](NO?)?·2MeCN (4), [Zn?(OH)?(L?)?](NO?)?·2MeOH·H?O (5) and [Zn?(OH)?(L?)?](NO?)?·3MeNO? (6) (where HL? = 2-iminomethyl-6-methoxy-phenol, HL? = 2-iminomethyl-4-bromo-6-methoxy-phenol). Each member exhibits a double-bowl pseudo metallocalix[6]arene topology whereby the individual [M?] units form molecular host cavities which are able to accommodate various guest molecules (MeCN, MeNO? and MeOH). Magnetic susceptibility measurements carried out on complexes 1 and 4 indicate weak exchange between the Ni(II) centres.     

Shape resonances in slow electron scattering by aromatic molecules. I. Anthraquinone derivatives

A series of anthraquinone (C(14)O(2)H(8)) derivatives has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), photoelectron spectroscopy (PES), and AM1 quantum chemical calculations. Mean lifetimes of molecular negative ions M(-.) (MNI) have been measured. The mechanism of long-lived MNI formation in the epithermal energy region of incident electrons has been investigated. A simple model of a molecule (a spherical potential well with the repulsive centrifugal term) has been applied for the analysis of the energy dependence of cross sections at the first stage of the electron capture process. It has been shown that a temporary resonance of MNI at the energy approximately 0.5 eV corresponds to a shape resonance with lifetime 1-2.10(-13) s in the f-partial wave (l = 3) of the incident electron. The next resonant state of MNI at the energy approximately 1.7 eV has been associated with the electron excited Feshbach resonance (whose parent state is a triplet npi* transition). In all cases the initial electron state of the MNI relaxes into the ground state by means of a radiationless transition, and the final state of the MNI is a nuclear excited resonance with a lifetime measurable on the mass spectrometry timescale. Copyright 1999 John Wiley & Sons, Ltd.     

Coordination-driven self-assembly directs a single-crystal-to-single-crystal transformation that exhibits photocontrolled fluorescence

Coordination-driven self-assembly is employed to direct a single-crystal-to-single-crystal [2 + 2] photodimerization that exhibits tunable fluorescence.     

A finite element formulation for global linear stability analysis of a nominally two‐dimensional base flow

A stabilized finite element method, to carry out the linear stability analysis of a two‐dimensional base flow to three‐dimensional perturbations that are periodic along span, is presented. The resulting equations for the time evolution of the disturbance requires a solution to the generalized eigenvalue problem. The analysis is global in nature and is also applicable to non‐parallel flows. Equal‐order‐interpolation functions for velocity and pressure are utilized. Stabilization terms are added to the Galerkin formulation to admit the use of equal‐order‐interpolation functions and to eliminate node‐to‐node oscillations that might arise in advection‐dominated flows. The proposed formulation is tested on two flow problems. First, the mode transitions in the circular Couette flow are investigated. Two scenarios are considered. In the first one, the outer cylinder is at rest, while the inner one spins. Two linearly unstable modes are identified. The primary mode is real and represents the axisymmetric Taylor vortices. The second mode is complex and consists of spiral vortices. For the counter‐rotating cylinders, the primary transition is via the appearance of spiral vortices. Excellent agreement with results from earlier studies is observed. The formulation is also utilized to investigate the parallel and oblique modes of vortex shedding past a cylinder for the Re = 100 flow. It is found that the flow is associated with a large number of unstable oblique shedding modes. The parallel mode of vortex shedding is a special case of this family of modes and is associated with the largest growth rate. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of acetaldehyde in liquid, solid and semi-solid food after pervaporation-derivatization

 A spectrophotometric method for the determination of acetaldehyde in liquid, semi-solid and solid food samples, employing the coupling of a continuous flow configuration to a pervaporation unit, has been proposed. It is based on the reaction of the analyte with fuchsin in acidic medium and subsequent formation of a coloured product (alkylsulphonic acid chromophore) with sodium sulphite, which was monitored spectrophotometrically. Variable sensitivity was obtained by altering the pervaporation temperature and the thickness of the membrane. The detection limits went down to 4.2 μg/mL and the precision was between 1.2 and 3.6%. Received: 5 August 1996/Revised: 16 October 1996/Accepted: 18 October 1996     

A highly porous interpenetrated metal-organic framework from the use of a novel nanosized organic linker

The initial use of a novel elongated tricarboxylic acid H(3)hmpib in metal-organic framework (MOF) chemistry resulted in a [Zn(4)O(hmpib)(2)] MOF (UCY-1) with pyrite topology. The compound displays a remarkably high internal surface area despite its double-interpenetrated structure as well as high CO(2) uptake and selective adsorption for it over CH(4).     

Hexa- and octanuclear iron(III) salicylaldoxime clusters

The syntheses, structures and magnetic properties of six iron complexes stabilised with the derivatised salicylaldoxime ligands Me-saoH(2) (2-hydroxyethanone oxime) and Et-saoH(2) (2-hydroxypropiophenone oxime) are discussed. The four hexanuclear and two octanuclear complexes of formulae [Fe(8)O(2)(OMe)(4)(Me-sao)(6)Br(4)(py)(4)]·2Et(2)O·MeOH (1·2Et(2)O·MeOH), [Fe(8)O(2)(OMe)(3.85)(N(3))(4.15)(Me-sao)(6)(py)(2)] (2), [Fe(6)O(2)(O(2)CPh-4-NO(2))(4)(Me-sao)(2)(OMe)(4)Cl(2)(py)(2)] (3), [Fe(6)O(2)(O(2)CPh-4-NO(2))(4)(Et-sao)(2)(OMe)(4)Cl(2)(py)(2)]·2Et(2)O·MeOH (4·2Et(2)O·MeOH), [HNEt(3)](2)[Fe(6)O(2)(Me-sao)(4)(SO(4))(2)(OMe)(4)(MeOH)(2)] (5) and [HNEt(3)](2)[Fe(6)O(2)(Et-sao)(4)(SO(4))(2)(OMe)(4)(MeOH)(2)] (6) all are built from a series of edge-sharing [Fe(4)(μ(4)-O)](10+) tetrahedra. Complexes 1 and 2 display a new μ(4)-coordination mode of the oxime ligand and join a small group of Fe-phenolic oxime complexes with nuclearity greater than six.     

Chiral single-molecule magnets: a partial Mn(III) supertetrahedron from achiral components

A [Mn(III)(9)] partial supertetrahedron is a Single-Molecule Magnet (SMM) with an energy barrier to magnetisation reversal of ~30 K and represents the first chiral SMM obtained from achiral starting materials.     

Pervaporation: An interface between fermentors and monitoring

An enzymic method for the determination of acetaldehyde applicable to the on-line monitoring of this analyte in fermentors has been proposed. The volatile analyte, after its separation by pervaporation, was collected in a stream containing NAD⁺, KC1 and 2-mercaptoethanol. The NADH formed was monitored spectrophotometrically at 340 nm. Different pervaporation temperatures were used, thus enlarging the determination range which was established between 1–100 μg ml⁻¹. The method, which provides excellent precision (RSD less than 3.5% in all instances) has been successfully applied to the determination of the analyte in spiked fermentation media.