Elvira M. Bauer

Tetrakis(selenodiazole)porphyrazines 1: Tetrakis(selenodiazole)porphyrazine and its Mg(II) and Cu(II) Derivatives. Evidence for their Conversion to Tetrakis(pyrazino)porphyrazines through Octaaminoporphyrazines

The new phthalocyanine-like macrocycle tetrakis(selenodiazole)porphyrazine, TSeDPzH2, and its Mg(II) and Cu(II) complexes have been prepared and their general, spectroscopic (IR, UV-vis), and magnetic properties investigated. It has been observed that the peripheral selenodiazole rings of the TSeDPz skeleton can be opened by the action of H2S, with release of the Se atoms and formation of a new macrocycle, i.e. octaaminoporphyrazine, which is easily converted into tetrakis(pyrazino)porphyrazine derivatives.

Versatile Synthesis of Carbon-Rich LiFePO4 Enhancing Its Electrochemical Properties

LiFePO 4 /C composites were prepared from thermal decomposition of Fe(II) organophosphonates Fe[(RPO 3 )(H 2 O)] (R = methyl or phenyl group) in the presence of Li 2 CO 3 at high temperature and under inert atmosphere. The compounds were characterized by chemical analysis, thermogravimetric analysis and differential scanning colorimetry, X-ray powder diffraction, and scanning electron microscopy. Electrodes were fabricated for the electrochemical characterization. The cathode material obtained from Fe[C 6 H 5 PO 3 (H 2 O)] showed a specific energy evaluated at C/10 rate of about 550 Wh kg - 1 . The specific power calculated at 30C rate in excess at 14,000 W kg - 1 , while the specific energy was about 28% of the theoretical one. No capacity fading was observed upon cycling.

Comparison of the structure and magnetic order in a series of layered Ni(II) organophosphonates, Ni[(RPO3)(H2O)] (R = C6H5, CH3, C18H37).

The reaction of nickel chloride with phenyl phosphonic acid under hydrothermal conditions resulted in the isolation of yellow-green single crystals of Ni[(C(6)H(5)PO(3))(H(2)O)]. The structure of the compound has been solved by X-ray single-crystal diffraction studies. Ni[(C(6)H(5)PO(3))(H(2)O)] crystallizes in the orthorhombic space group Pmn2(1) and is isostructural with the Mn(II), Fe(II), and Co(II) analogues. It presents the typical features of the hybrid 2D structures, consisting of alternating inorganic and organic layers. The former are formed by six-coordinated nickel(II) ions bridged by oxygen atoms into the layers. The inorganic layers are capped by the phenyl phosphonate groups, with phenyl groups of two adjacent ligands forming a hydrophobic bilayer region, and van der Waals contacts are established between them. The magnetic properties investigated by means of dc and ac susceptibility measurements point to an AF exchange coupling between nearest neighboring Ni(II) ions. Below 5 K, the compound orders magnetically showing the typical features of a canted antiferromagnet. The magnetic behavior and magnetic dimensionality of Ni[(C(6)H(5)PO(3))(H(2)O)] have been fully analyzed and compared to those of the Ni(II) parent compounds Ni[(RPO(3))(H(2)O)] (where R = CH(3), C(18)H(37)), which exhibit different symmetries of the inorganic layers and lengths of the R groups.

A Novel 1D-AF Hybrid Organic-Inorganic Chromium(II) Methyl Phosphonate Dihydrate: Synthesis, X-Ray Crystal and Molecular Structure, and Magnetic Properties

Light-blue crystals of chromium(II) methyl phosphonate dihydrate, [Cr(CH(3)PO(3))(H(2)O)].H(2)O, were obtained in water by mixing filtered solutions of methylphosphonic acid and chromium(II) chloride in the presence of urea in an inert atmosphere. The compound was characterized by elemental analysis, TGA-DSC, X-ray crystallography, magnetic measurements, and UV-visible and FT-IR spectroscopies. The crystal and molecular structures (orthorhombic Pnma (no. 62): a = 4.4714(5) A, b = 6.8762(7) A, c = 19.180(2) A, Z = 4) have been solved using single-crystal X-ray diffraction. The chromium(II) ion is six-coordinated by oxygens (4 + 2) to form an elongated octahedron, with the four equatorial oxygen atoms belonging to [-PO(3)](2-) phosphonate groups. This stereochemistry of the Cr(II) ion (high-spin d(4) electronic configuration) is ascribed to the Jahn-Teller effect. The [CrO(6)] chromophore, the [CH(3)PO(3)](2-) anions, and the water molecules build a novel one-dimensional (1D) metal(II) oxide chain, anchored to each other within the ab plane by two oxygens of the phosphonate ligand. Within the chain, each Cr(2+) ion is connected through double oxygen bridges to its two neighbors, forming edge-sharing octahedra running along the b axis. The chains are further connected with the adjacent chains by phosphonate [-PO(3)](2-) groups of the ligand, forming an inorganic layer that alternates along the c axis of the unit cell with bilayers, consisting of methyl groups and water of crystallization. The thermal variation of the magnetic susceptibility follows the Curie-Weiss law, with a large negative Weiss constant, theta = -60 K, indicating the presence of antiferromagnetic AF exchange interactions between neighboring Cr(II) ions. The magnetic behavior and the magnetic dimensionality have been analyzed in terms of Fishers classical limiting form of the Heisenberg chain theory, and a value of J = -9.3 cm(-1) was found. The negative value of the intra-chain exchange constant coupling J confirms the presence of an AF coupling. No sign of long-range magnetic ordering down to 2 K (the lowest measured temperature) is observed, in agreement with the predominant one-dimensional character of the exchange interactions.

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.

Synthesis, Characterization, and Electrochemical Behavior of LiMnxFe(1−x)PO4 Composites Obtained from Phenylphosphonate-Based Organic-Inorganic Hybrids

The synthesis of organic-inorganic hybrid compounds based on phenylphosphonate and their use as precursors to form LiMnxFe(1−x)PO4 composites containing carbonaceous substances with sub-micrometric morphology are presented. The experimental procedure includes the preliminary synthesis of Fe2+ and/or Mn2+ phenylphosphonates with the general formula Fe(1−x)Mnx[(C6H5PO3)(H2O)] (with 0 < x < 1), which are then mixed at different molar ratios with lithium carbonate. In this way the carbon, obtained from in situ partial oxidation of the precursor organic part, coats the LiMnxFe(1−x)PO4 particles. After a structural and morphological characterization, the electrochemical behavior of lithium iron manganese phosphates has been compared to the one of pristine LiFePO4 and LiMnPO4, in order to evaluate the doping influence on the material.

Ni(II)octadecylphosphonate: an inorganic/organic layered weak-ferromagnet

Ni[CH3(CH2)17PO3]/H2O was prepared and characterized by several techniques and the magnetic properties were measured by using a SQUID magnetometer. Preliminary refinement of the X-ray diffraction powder data by structure-less Le Bail fitting could be obtained and the compound was found to crystallise in the orthorhombic space group Pmn21 with a � /5.478(7) A ˚ , b � /42.31(4) A ˚ , c � /4.725(3) A ˚ . Ni(II)octadecyl phosphonate is lamellar and the structure consists of alternating inorganic and organic layers. The inorganic layers are interspersed by by-layers of the octadecyl substituent and van der Waals contacts are established between them. IR spectroscopy revealed all-trans configuration of the hydrocarbonic chain. A tilt angle of 48.28 between the chain axis and the (ac ) plane could be estimated. The temperature dependence of the molar susceptibility plotted as 1/x vs. T is linear above 100 K and it follows the Curie � /Weiss law. The Curie, C , constant suggests the presence of Ni(II) ion in the S � /1 spin state and the negative Weiss, u , constant is indicative of antiferromagnetic nearest neighbour exchange interactions. Zero-field and field-cooled x vs. T plots were then recorded. The plots show no overlap below 20 K, thus indicating that the compound is in an ordered magnetic state. The critical temperature has been located at the onset of the x vs. T plot and was found to be TN � /21 K. The magnetization vs. field plots, measured at different temperatures, provide the indication that the compound is a weak-ferromagnet below TN. # 2003 Elsevier Science Ltd. All rights reserved.

Performances of an electrochromic device based on WO3 oxide and Ce-V mixed oxide thin films

The aim of this work is to check the possibility of using originally developed thin films of mixed oxides of cerium and vanadium as ion storage electrode within an electrochromic cell. Transmittance variation as function of the amount of lithium exchanged between the WO3 film and the Ce-V oxide film has been measured in the visible and near IR spectrum. Also real time single wavelength measurements have been performed in different conditions to test the speed of coloration.

Oxide films made by radio frequency sputtering of solid and powder targets : a comparison

Cathode sputtering is a well-known technique for deposition of thin films starting from metallic or ceramic materials. Ceramic insulating materials are usually sputtered using radio frequency as electric power source. In this work we compare the optical properties of tin films deposited from two different types of targets. The first set of samples was deposited from solid targets glued to a water-cooled back- plate. For the second set we used targets made of cold pressed powders of the corresponding materials. The possibility of sputtering from weakly pressed powders can be favorably exploited to develop mixed materials. Their cost, in fact, is about one tenth of glued solid targets, and mixtures of any required composition can be quickly prepared. Two oxides, SiO2 and Al2O3 have been deposited by both methods in the same deposition chamber, using the same process parameters, and sputtering gas. Their optical characteristics - refractive index and extinction coefficient - have been compared over the VIS-NIR spectral range.