Polynuclear lanthanide complexes of a series of bridging ligands containing two tridentate N,N',O-donor units: structures and luminescence properties

A set of three potentially bridging ligands containing two tridentate chelating N,N',O-donor (pyrazole-pyridine-amide) donors separated by an o, m, or p-phenylene spacer has been prepared and their coordination chemistry with lanthanide(III) ions investigated. Ligand L(1) (p-phenylene spacer) forms complexes with a 2:3 M:L ratio according to the proportions used in the reaction mixture; the Ln(2)(L(1))(3) complexes contain two 9-coordinate Ln(III) centres with all three bridging ligands spanning both metal ions, and have a cylindrical (non-helical) 'mesocate' architecture. The 1:1 complexes display a range of structural types depending on the conditions used, including a cyclic Ln(4)(L(1))(4) tetranuclear helicate, a Ln(2)(L(1))(2) dinuclear mesocate, and an infinite one-dimensional coordination polymer in which metal ions and bridging ligands alternate along the sequence. ESMS studies indicate that the 1:1 complexes form a mixture of oligonuclear species {Ln(L(1))}(n) in solution (n up to 5) which are likely to be cyclic helicates. In contrast, ligands L(2) and L(3) (with o- and m-phenylene spacers, respectively) generally form dinuclear Ln(2)L(2) Ln(III) complexes in which the two ligands may be arranged in a helical or non-helical architecture about the two metal ions. These complexes also contain an additional exogenous bidentate bridging ligand, either acetate or formate, which has arisen from hydrolysis of solvent molecules promoted by the Lewis-acidity of the Ln(III) ions. Luminescence studies on some of the Nd(III) complexes showed that excitation into ligand-centred pi-pi* transitions result in the characteristic near-infrared luminescence from Nd(III) at 1060 nm.     

Fluorescence amplification by electrochemically deposited silver nanowires with fractal architecture

Electrochemically deposited silver structures with nanowires 50-100 nm in diameter show high fluorescence amplification and strongly reduced fluorescence lifetimes. Both quantities depend on the structure thickness. With increasing thickness the fluorescence amplification proportionally increases and the fluorescence lifetime decreases. This thickness dependence is caused by fluorophore interaction with a system of plasmon excitations in coupled nanowires extending over micrometer size regions. Thus the amplification is attributed to a combination of extended structure area and strong plasmonic coupling between nanowires which also help to radiatively scatter the fluorescence emission.     

Saari's conjecture is true for generic vector fields

The simplest non-collision solutions of the -body problem are the ``relative equilibria', in which each body follows a circular orbit around the centre of mass and the shape formed by the bodies is constant. It is easy to see that the moment of inertia of such a solution is constant. In 1970, D. Saari conjectured that the converse is also true for the planar Newtonian -body problem: relative equilibria are the only constant-inertia solutions. A computer-assisted proof for the 3-body case was recently given by R. Moeckel, Trans. Amer. Math. Soc. (2005). We present a different kind of answer: proofs that several generalisations of Saari's conjecture are generically true. Our main tool is jet transversality, including a new version suitable for the study of generic potential functions.

     

Study of acid-base properties of a SiO2?AlPO4 (80∶20 W/W) catalyst

2-Methyl-3-butyn-2-ol (MBOH) transformation was used as a test reaction in order to determine the acid-base properties of a SiO₂/AlPO₄ (80∶20 w/w) catalyst. Experiments were carried out in a microcatalytic pulse reactor and in a continuous-flow reactorvia Temperature Programmed Surface Reactions-Mass Spectrometry (TPSR-MS). Results are compared to acid-base properties calculated by other instrumental techniques.     

Relatively Stable Bundles over Elliptic Fibrations

We consider a relative Fourier‐Mukai transform de.ned on elliptic fibrations over an arbitrary base scheme. This is used to construct relative Atiyah sheaves and generalize Atiyah and Tu's results about semistable sheaves over elliptic curves to the case of elliptic fibrations. Moreover we show that this transform preserves relative (semi)stability of sheaves of positive relative degree.     

Simulation of Fibrillation of PC/LCP/Kevlar Blends and Its Characterizations

Kevlar fiber was fluorinated and oxy-fluorinated directly in presence of undiluted fluorine and fluorine gas mixture and processed with Polycarbonate and LCP at 320 °C under 20 rpm in a twin-screw extruder. The composites were then injection molded into dumbbell shaped specimens under different conditions like various mold temperatures, injection temperatures, injection speeds and mold filling rates. Various physico-chemical characterizations have been performed under definite processing parameter. Orientation of fibers under different injection parameters was evaluated using mold flow simulation technique. Most injection molded or extruded structures however, exhibit non-uniform fiber orientation across the final parts, with a diverging variety of different local fiber orientation states. Distinct skin and core regions were observed in the injection molded parts and it has also been found out that fiber orientation is different in skin and core region for both unmodified and modified derivative, which affects the flow behavior. Processing parameters significantly affect the fiber orientation pattern in the skin and core region for all blended materials. It is worth mentioning that the maximum fiber orientation occurred during the extrusion process at the wall but different extent of fiber orientation is observed during the injection molding depending on the shape of the dumbbell specimen. This fibrillation has been corroborated by the SEM study in both the skin and core region.     

Leptogorgolide, a biogenetically interesting 1,4-diketo-cembranoid that reinforces the oxidation profile of C-18 as taxonomical marker for octocorals

The cembranoid 1 and the furanocembranolides 2-4 along with the known pukalide were isolated from Leptogorgia sp. and their structures determined spectroscopically. The 1,4-diketo-cembranoid 1 follows an oxidation pattern of C-18 that reinforces the concept of oxidation profile of C-18 as taxonomical marker for octocorals. The co-occurrence within a species of furanocembranolide/1,4-diketo-cembranoid congeners 1/2-4 raises the question about which one is the biogenetic precursor. A biogenetic pathway is proposed.     

Flux growth and structure of two compounds with the EuIn2P2 structure type,AIn2P2 (A = Ca and Sr), and a new structure type,BaIn2P2

Single crystals of the new Zintl phases AIn₂P₂ [A = Ca (calcium indium phosphide), Sr (strontium indium phosphide) and Ba (barium indium phosphide)] have been synthesized from a reactive indium flux. CaIn₂P₂ and SrIn₂P₂ are isostructural with EuIn₂P₂ and crystallize in the space group P6₃/mmc. The alkaline earth cations A are located at a site with m symmetry; In and P are located at sites with 3m symmetry. The structure type consists of layers of A²⁺ cations separated by [In₂P₂]²⁻ anions that contain [In₂P₆] eclipsed ethane‐like units that are further connected by shared P atoms. This yields a double layer of six‐membered rings in which the In—In bonds are parallel to the c axis and to one another. BaIn₂P₂ crystallizes in a new structure type in the space group P2₁/m with Z = 4, with all atoms residing on sites of mirror symmetry. The structure contains layers of Ba²⁺ cations separated by [In₂P₂]²⁻ layers of staggered [In₂P₆] units that form a mixture of four‐, five‐ and six‐membered rings. As a consequence of this more complicated layered structure, both the steric and electronic requirements of the large Ba²⁺ cation are met.     

Effective elastic properties of 3D polypropylene microstructures of an injection moulded plate via different homogenization schemes

The mechanical properties of a polypropylene (PP) part depend on its morphology and degree of crystallinity. To evaluate its effective elastic behaviour two upscaling schemes are developed and compared. In the 1^st method the spherulites are assumed to be isotropic and vary linearly with the spherulite diameter. In the 2^nd one, the homogenization is performed successively on two scales. At the nanoscale, the bilamina of amorphous and crystalline phases is homogenized. Then, at the microscale, a 3D radial distribution of effective bilamina is homogenized. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)