Single and Double Ionization of Corannulene and Coronene

Electron‐transfer processes that involve single and doubly charged cations of corannulene (C₂₀H₁₀) and coronene (C₂₄H₁₂) are examined by three different mass‐spectrometric techniques. Photoionization studies give first‐ionization energies of IE(C₂₀H₁₀)=7.83±0.02 eV and IE(C₂₄H₁₂)=7.21 ±0.02 eV. Photoionizations of the neutrals to the doubly charged cations occur at thresholds of 20.1±0.2 eV and 18.5±0.2 eV for corannulene and coronene, respectively. Energy‐resolved charge‐stripping mass spectrometry yields kinetic energy deficits of Q_min(C₂₀H=13.8±0.3 eV and Q_min(C₂₄H=12.8±0.3 eV for the transitions from the mono‐ to the corresponding dications in keV collisions. Reactivity studies of the C₂₀H and C₂₄H dications in a selected‐ion flow‐tube mass spectrometer are used to determine the onsets for the occurrence of single‐electron transfer from several neutral reagents to the dications, affording two different monocationic products. With decreasing IEs of the neutral reagents, electron transfer to doubly charged corannulene is first observed with hexafluorobenzene (IE=9.91 eV), while neutrals with lower IEs are required in the case of the coronene dication, e.g., NO₂ (IE=9.75 eV). Density‐functional theory is used to support the interpretation of the experimental data. The best estimates of the ionization energies evaluated are IE(C₂₀H₁₀)=7.83±0.02 eV and IE(C₂₄H₁₂)=7.21 ±0.02 eV for the neutral molecules, and IE(C₂₀H)=12.3±0.2 eV and IE(C₂₄H)=11.3±0.2 eV for the monocations.     

Thermal behavior of the coordination compound [Co(urea)6](NO3)2

The coordination compound [Co(urea)₆](NO₃)₂ was synthesized and physico-chemically characterized. The thermal decomposition carried out in dynamic air and inert atmosphere under non-isothermal conditions has been investigated by means of combined thermogravimetry/mass spectrometry, X-ray diffraction, IR and UV-VIS spectroscopy as well as magnetic measurements. The course of the thermal decomposition starts with two-phase transitions (melting and a O_h→T_dconfiguration change of the Co²⁺ ion) and continues with seven mass loss steps. According to the thermogravimetric and magnetic investigations a dimeric compound, [Co(biuret)(NCO)]₂(NO₃)₂, is assumed to arise. Up ~250°C, an oxohydroxide nitrate intermediate is formed and a gradual oxidation of the Co²⁺ ions is observed. At 550°C, Co₃O₄ with mean crystallite sizes of ~150 Ĺ is identified. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal behaviour of some Al(III)-Mg(II) polynuclear coordination compounds with polycarboxylic acid anions as ligands,precursors of aluminates

A TG, DTG and DTA study of three polynuclear coordination compounds,containing Al(III)-Mg(II), namely (NH₄)₄[Al₂Mg(C₄O₅H₄)₄(OH)₄]?2H₂O,(NH₄)₄[MgAl₂(C₄H₄O₆)₄(OH)₄]?3H₂Oand (NH₄)₂[Al₂Mg(C₆O₇H₁₁)₅(OH)₅]?3H₂O,has been reported together with the associated thermal decomposition mechanismrationalized in terms of intermediate products. As decomposition end-product,magnesium-aluminum spinel is obtained. The values of MgAl₂O₄mean crystallite size depend on the anionic ligand contained by the precursorcompound, varying in the order: malate (143 Å) ligand contained by theprecursor compound, varying in the order: malate (143 Å)     

Thermal investigations of nickel–zinc ferrites formation from malate coordination compounds

Nickel–zinc ferrites have been synthesized via thermal decomposition of polynuclear coordination compounds containing as ligand the anion of malic acid, namely (NH₄)[Fe₂NixZn_1–x(C₄H₄O₅)(OH)₃]·nH₂O (x =0.25, 0.5 and 0.75, n=3 and 5). A comparison between the thermal behaviour of the studied polynuclear coordination compounds is inferred. Fe₂NixZn_1–xO₄ (n=0.25, 0.5 and 0.75) ferrites with mean particle sizes of 65–85 Å and free from other phases are formed after a heating treatment of only one hour at 500°C.     

Homogenization of a Ginzburg–Landau functional

We consider a nonlinear homogenization problem for a Ginzburg–Landau functional with a (positive or negative) surface energy term describing a nematic liquid crystal with inclusions. Assuming that sizes and distances between inclusions are of the same order ?, we obtain a limiting functional as $?\to 0$. We generalize the method of mesocharacteristics to show that a corresponding homogenized problem for arbitrary, periodic or non-periodic geometries is described by an anisotropic Ginzburg–Landau functional. We give computational formulas for material characteristics of an effective medium. To cite this article: L. Berlyand et al., C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

Iron,nickel and zinc malates coordination compounds cynthesis,characterization and thermal behaviour

The coordinations compounds (NH₄)[Fe(C₄H₄O₅)(OH)₂]·0.5H₂O, [Ni(C₄H₄O₅)]·3H₂O and [Zn(C₄H₄O₅)]·5H₂O were synthesized by a precipitation method and characterized by chemical analysis, spectral (IR, UV-VIS) and magnetical investigations. In the range 50-600°C stepped thermal decompositions occur with formation of anhydrous malates, malonates, oxoacetates (iron and nickel compounds) and hydroxocarbonate (Zn compound) as intermediates observed by FT-IR spectroscopy. α-Fe₂O₃, NiO and ZnO constitute the final decomposition products. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis,characterization, molecular docking studies and in vitro screening of new metal complexes with Schiff base as antimicrobial and antiproliferative agents

A series of Cu(II), Co(II), Pd(II), Pt(II), Zn(II), Cd(II) and Fe(III) complexes were designed and synthesized using Schiff base 1‐phenyl‐2,3‐dimethyl‐4‐(N‐3‐formyl‐6‐methylchromone)‐3‐pyrazolin‐5‐one (HL). The new metal complexes were investigated using various physicochemical techniques including elemental and thermal analyses, molar electric conductivity and magnetic susceptibility measurements, as well as spectroscopic methods. Also, the crystal structures of ligand HL and the Pd(II) complex were determined using single‐crystal X‐ray diffraction analysis. For all compounds, the antimicrobial activity was studied against a series of standard strains: Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, Escherichia coli, Acinetobacter baumannii, Candida albicans, Candida krusei and Cryptococcus neoformans. The in vitro antiproliferative activity of the ligand and complexes was evaluated against ten cancer cell lines: MSC, A375, B16 4A5, HT‐29, MCF‐7, HEp‐2, BxPC‐3, RD, MDCK and L20B. At 10 μM concentration a significant cytotoxic effect of the Co(II), Pd(II) and Cd(II) complexes was observed against B16 4A5 murine melanoma cells. The Zn(II) complex is active against HEp‐2, RD and MDCK cancer cell lines, where IC₅₀ values vary between 1.0 and 77.6 and for BxPC‐3 the activity index versus doxorubicin is 3.7 times higher.     

Thermal stability of amino acid-(tyrosine and tryptophan) coated magnetites

The thermal stability of two amino acid-(tyrosine and tryptophan) coated magnetite and their corresponding precursors, [Fe₂^IIIFe^II(Tyr)₈]·9H₂O and [Fe₂^IIIFe^II(Trp)₂(OH)₄](NO₃)₂·8H2O (where tyrosine=Tyr and tryptophan=Trp), was analyzed in comparison with free amino acids. The complexes present a lower thermal stability relative to the free ligand, due to the catalytic effect introduced by the iron cation and the presence of NO₃⁻ groups. The presence of NO₃⁻ group determines also a different degradation’s stoichiometry of the amino acid anion comparative with the one expressed by the free ligand molecule. The amino acid bonded to magnetite decomposes in two steps, its presence inducing an increasing of γ-Fe₂O₃→Fe₂O₃ conversion temperature.     

Recent advances in amino acid analysis by capillary electrophoresis

This paper describes the most important articles that have been published on amino acid analysis using CE during the period from June 2009 to May 2011 and follows the format of the previous articles of Smith (Electrophoresis 1999, 20, 3078-3083), Prata et al. (Electrophoresis 2001, 22, 4129-4138) and Poinsot et al. (Electrophoresis 2003, 24, 4047-4062; Electrophoresis 2006, 27, 176-194; Electrophoresis 2008, 29, 207-223; Electrophoresis 2010, 31, 105-121). We present new developments in amino acid analysis with CE, which are reported describing the use of lasers or light emitting diodes for fluorescence detection, conductimetry electrochemiluminescence detectors, mass spectrometry applications, and lab-on-a-chip applications using CE. In addition, we describe articles concerning clinical studies and neurochemical applications of these techniques.     

Thermal behaviour and electro-optical properties of a series of liquid crystals based on palladium complexes with mixed ligands

A series of ortho-metallated palladium(II) complexes with two dimeric liquid crystals Schiff base (methoxy and decyloxy as terminal groups) as cyclometallated ligands and N-aryl-N′-benzoyl thiourea derivatives as co-ligands were prepared and investigated for their liquid crystalline properties. Their structures were assigned based on elemental analysis, FT-IR and ¹H NMR spectroscopy while the thermal behaviour was investigated by differential scanning calorimetry and polarising optical microscopy. The complexes with Schiff base ligand bearing methoxy group as terminal group show extensive decomposition during melting while the complexes with Schiff base having decyloxy group as terminal group show monotropic nematic phases, with the mesophase stability strongly related to the type of N-aryl-N′-benzoyl thiourea derivative used. Their liquid crystalline properties are compared with their analogues having N,N-dialkyl-N′-benzoyl thiourea as co-ligands which were reported previously. One of the latter complexes was also investigated by thermally stimulated depolarisation currents method while the optical transmission was recorded simultaneously. The thermally stimulated depolarisation currents and optical transmission spectra confirmed the previous observation regarding the phase transition temperatures. The current intensity–applied voltage dependencies of this complex were investigated by specific electrical measurements.