Nickel(II) 3,4;9,10-perylenediimide bis-phosphonate pentahydrate: a metal-organic ferromagnetic dye

The new metal-organic compound nickel(II) 3,4;9,10-perylenediimide bis-phosphonate pentahydrate, i.e. Ni(2)[(PDI-BP)(H(2)O)(2)]·3H(2)O (1), has been synthesized and its structural and magnetic properties have been studied. Reaction of 3,4;9,10-perylenediimide bis-phosphonate (PDI-BP, hereafter) ligand and nickel chloride in water resulted in the precipitation of a red and poorly crystalline solid (1). As the solid shows a poor crystalline organization of aggregates, the energy dispersive X-ray diffraction analysis (EDXD) technique has been used to obtain short-range order structural information of the single nanoaggregates by radial distribution function analysis. The overall structure of the compound is characterized by layers containing perylene planes shifted in the direction perpendicular to the stacking axes in such a way that only the outer rings overlap. The edges of the perylene planes are connected to the phosphonate groups through an imido group. The oxygen atoms of the [-PO(3)](2-) group and those of the water molecules are bonded to the nickel ions resulting in a [NiO(6)] octahedral coordination sphere. The Ni-O bond lengths are 0.21 ± 0.08 nm and the Ni-O-Ni angles of aligned moieties are 95 ± 2°. The oxygen atoms of the water molecules and the nickel atoms are nearly planar and almost perpendicular to the perylene planes forming chains of edge-sharing octahedra. The magnetic properties of (1) show the presence of intrachain ferromagnetic Ni-Ni interactions and a long-range ferromagnetic order below 21 K with a canting angle and with a spin glasslike behavior due to disorder in the inorganic layer. Hysteresis cycles show a coercive field of ca. 272 mT at 2 K that decreases as the temperature is increased and vanishes at ca. 20 K.     

On the computation of the rank of block bidiagonal Toeplitz matrices

In the present paper we study the computation of the rank of a block bidiagonal Toeplitz (BBT) sequence of matrices. We propose matrix-based, numerical and symbolical, updating and direct methods, computing the rank of BBT matrices and comparing them with classical procedures. The methods deploy the special form of the BBT sequence, significantly reducing the required flops and leading to fast and efficient algorithms. The numerical implementation of the algorithms computes the numerical rank in contrast with the symbolical implementation, which guarantees the computation of the exact rank of the matrix. The combination of numerical and symbolical operations suggests a new approach in software mathematical computations denoted as hybrid computations.     

Self-adjoint extensions and unitary operators on the boundary

We establish a bijection between the self-adjoint extensions of the Laplace operator on a bounded regular domain and the unitary operators on the boundary. Each unitary encodes a specific relation between the boundary value of the function and its normal derivative. This bijection sets up a characterization of all physically admissible dynamics of a nonrelativistic quantum particle confined in a cavity. Moreover, this correspondence is discussed also at the level of quadratic forms. Finally, the connection between this parametrization of the extensions and the classical one, in terms of boundary self-adjoint operators on closed subspaces, is shown.     

Hybrid polymer inorganic materials prepared from ternary microemulsions

The microemulsion system containing vinyl acetate (Vac), silane derivatives tetraethoxysilane (TEOS), methacryloxypropyltrimethoxysilane (MPTS), vinyltriethoxysilane (VTES), methyltriethoxysilane (MeTES), octyltriethoxysilane (OTES), nonylphenol etoxylated with 25 mol of ethylene oxyde (NPEO₂₅) and water was studied. It was established that the probability of microemulsion formation increases with surfactant concentration. The microenviroment of the solubilization of the VAc and of silane derivatives in the aggregates of NPEO₂₅ was affected by their polarity. Hybrid materials were obtained by sol-gel reaction of silane derivatives combined with free-radical polymerization of VAc. The change of the glass transition temperature and of thermal stability of the polymer chains in the presence of the inorganic one proved the formation of simultaneous polymer inorganic hybrids.     

X‐ray fluorescence analysis on a group of coins from the ancient roman city of Tridentum (Trento,Italy)

A group of 83 coins, found in the archeological excavations of the ancient Roman city of Tridentum (Trento, Italy), was studied for the determination of their composition, finalized to their classification and cataloging. The coins, mainly made of copper‐based alloys, were minted between the republican period (II century BC) and the last decades of the western empire (V century AD). The X‐Ray Fluorescence archaeometric analysis has allowed a revision of the typological classification of the coins through the identification of six broad groups, each one characterized by a peculiar composition of the coins in the group. A tentative assignation of all the unreadable coins to one of the groups identified was proposed, in a way that could suggest also a possible dating of these coins. Copyright © 2014 John Wiley & Sons, Ltd.     

Hamburger and Stieltjes moment problems in several variables

In this paper we give solutions to the Hamburger and Stieltjes moment problems in several variables, in algebraic terms, via extended sequences. Some characterizations of the uniqueness of the solutions are also presented.

     

Spectroscopic study on nystatin conformational modifications generated by its interaction with the solvent

Conformational transformations of the tetraenic nystatin chromophore under the influence of solvents and UV irradiation have been studied by absorption, fluorescence and wide-line NMR spectroscopy.     

Synthesis of new 3,5-diarylisoxazolidines by cycloaddition of oxaziridines and alkenes

This article reports a novel process of cycloaddition of C-aryloxaziridines with a variety of alkenes to afford stable, five-membered heterocycles 13–24. The steric hindrance of the tert-butyl group on the nitrogen atom of the oxaziridine is responsible for the high stereoselectivity of the cycloaddition reaction.     

Guerbet condensation of methanol with n-propanol to isobutyl alcohol over heterogeneous copper chromite/Mg–Al mixed oxides catalysts

The synthesis of isobutyl alcohol (ⁱBuOH) from methanol (MeOH) and n-propanol (PrOH) through the Guerbet condensation has been studied at 200 °C and under inert atmosphere (3.0 MPa of N₂), using a two-component heterogeneous catalytic system based on pre-activated copper chromite and Mg–Al mixed oxides deriving from hydrotalcite-type (HT) precursors with different Mg/Al ratios. All the investigated catalysts displayed a significant activity, with an almost complete selectivity to ⁱBuOH. Unlike the copper chromite/soluble sodium methoxide system, the catalysts were tolerant of the co-produced water and did not display any appreciable deactivation during the course of the reaction. The catalyst productivity was found to increase by reducing the Mg/Al ratio in the heterogeneous base, according to the increase of the fraction of medium–strong and strong basic sites which favour the aldol condensation between the aldehydes derived from MeOH and PrOH.