Crystal Structure and Superoxide Dismutase Activity of [Cu(ethylenediamine)<Subscript>2</Subscript>Cl][PF<Subscript>6</Subscript>]

Summary. The preparation, spectroscopic properties, and crystal structure of chlorobis(ethylenediamine)copper(II) hexafluorophosphate [Cu(en)₂Cl][PF₆], (en=ethylendiamine) are reported. The complex crystallizes in the monoclinic system, space group P2₁/c, with cell constants a=6.1488(9) Å, b=12.696(2) Å, c=17.7424(17) Å, =97.265(12)°, and Z=4. The copper(II) ion is coordinated to two bidentate en molecules, to one chlorine ion, and to a more distant fluorine atom of the PF₆ group, leaving the copper ion in a distorted octahedral coordination geometry. The superoxide dismutase mimetic activity of the complex was investigated using the indirect xanthine-xanthine oxidase- nitroblue tetrazolium method and compared to that of the native enzyme.     

Debundling and dissolution of single-walled carbon nanotubes in amide solvents

Wet chemical methods involving ultrasound and amide solvents were used to purify and separate large bundles of single-walled carbon nanotubes (SWNTs) into individual nanotubes that could then be transported to silicon or mica substrates. The SWNTs studied were produced by the arc-discharge process. Dry oxidation was used in an initial step to remove amorphous carbon. Subsequently, two acid purification schemes were investigated (HCl- and HNO(3)-reflux) to remove the metal growth catalyst (Ni-Y). Finally, ultrasonic dispersion of isolated tubes into either N,N-dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP) was carried out. Raman scattering, atomic force microscopy (AFM), and electron microscopy were used to study the evolution of the products. Raman scattering was used to probe possible wall damage during the chemical processing. We found that both HCl and HNO(3) could be used to successfully remove the Ni-Y below approximately 1 wt %. However, the HNO(3)-reflux produced significant wall damage (that could be reversed by vacuum annealing at 1000 degrees C). In the dispersion step, both amide solvents (DMF and NMP) produced a high degree of isolated tubes in the final product, and no damage during this dispersion step was observed. HNO(3)-refluxed tubes were found to disperse the best into the amide solvents, perhaps because of significant wall functionalization. AFM was used to study the filament diameter and length distributions in the final product, and interesting differences in these distributions were observed, depending on the chemical processing route.     

Biscavitands II: Self-Inclusion in a Back-to-Back Connected Biscavitand

A foot-to-foot or `back-to-back' connected biscavitand is prepared directly from a hexadecol resorcinarene precursor. The axial orientation of the biphenyl linker and hence the crown conformation of the hexadecol was established by an X-ray crystal study of the biscavitand. Each cavitand bowl is filled in the crystal by an alkyl `foot' from the next molecule, a self-inclusion which results in polymeric host–guest chains. The new biscavitand differs from previously prepared Z and C isomers of a bowl-to-bowl or `front-to-front' connected host, which crystallize as chains of carcerand-like, solvent-filled cages or as distinct molecules of hemicarceplex, respectively.     

Identification of iridoid and sesquiterpenes from <Emphasis Type="Italic">Buddleia parviflora</Emphasis> by NMR spectra

A new compound was elucidated as 9-acetyl-6-caryophyllen-15-ol. Iridoid glucosides including catalpol, methyl catalpol, 7-deoxy-8-epiloganic acid, and aucubin, were isolated from leaves of Buddleia parviflora, while the known compounds were identified as dehydrobuddledin A and buddledin C. The structures was elucidated by extensive 1D-2D-NMR spectroscopy. Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 29–31, January–February, 2008.     

Modeling diamagnetic and magnetooptic properties of organic compounds with the TOSS-MODE approach

The topological substructural molecular design (TOSS-MODE) approach is used to describe the diamagnetic susceptibility of organic compounds. Two data sets composed of 233 aliphatic and 85 aromatic compounds were studied for which good linear correlations were found. The contributions of many different structural fragments and atomic groups were computed by the current approach. The predictive ability of the models developed was tested by using external prediction sets of compounds of different classes than those used in training. A quantitative model based on the current approach was developed to compute the diamagnetic susceptibility exaltation of aromatic compounds, which is exemplified by the study of polycyclic aromatic hydrocarbons. The rotatory power of organic compounds in a magnetic field was also described by the TOSS-MODE approach. Good linear correlations were obtained for this property in aliphatic and aromatic compounds. The predictive abilities of the models found were tested by external prediction sets for which good correlations between calculated and experimental values are found.     

Thermoluminescence glow curves analysis of pure and CeO2-doped Li2O-Al2O3-SiO2 glass ceramics

A comparative study of the thermoluminescence (TL) emission between beta-irradiated lithium aluminosilicates, Li₂O-Al₂O₃-SiO₂ (LAS), and beta-irradiated CeO₂-doped lithium aluminosilicates, Li₂O-Al₂O₃-SiO₂-CeO₂ (LAS:Ce), grown by sol-gel technique and preannealed at 1250 °C is presented. It is found that doping reinforces the result of preannealing the sample; the incorporation of CeO₂ at low concentrations shifts the TL curves towards higher temperatures and increases the total intensity with respect to samples without the dopant. This behavior, together with the fact that CeO₂ is a good densification agent, suggests the possibility of using CeO₂ to improve the technological properties of LAS. Deconvolution analysis of the thermoluminescence glow curves of doped materials under general order kinetics shows that the relevant temperatures at which the component signals appear are virtually the same as for pure samples. This suggests that CeO₂ does not introduce new types of traps, but only changes the population and distribution of impurities responsible for the TL in the original matrix of LAS. Finally, the kinetic parameters for the deconvoluted curves are reported. They corroborate that changes in CeO₂ concentration only vary the depth and distribution of the same kind of original traps.     

Nuclear and magnetic order in Y(Ni,Mn)O3 manganites by neutron powder diffraction

Neutron powder diffraction experiments performed on two selected compositions of the yttrium-based solid solution YNi_xMn_1−xO₃ clearly reveal a nuclear order between the Ni²⁺ and Mn⁴⁺ ions in the half-substituted compound YNi_0.50Mn_0.50O₃, so that the crystal structure is no longer described in the conventional orthorhombic Pbnm space group, but in the monoclinic P2₁/n, all over the investigated temperature range (1.5-300 K). However, both X-rays diagrams and neutron patterns of the YNi_0.25Mn_0.75O₃ phase are indexed in the Pbnm orthorhombic-like symmetry, indicating that the Mn and Ni ions are randomly distributed on the octahedral sites.In addition, neutron diffraction points out that the nature of the magnetic ordering is strongly connected to the structural properties. Whereas no long-range 3D-magnetic ordering was detected for the Pbnm YNi_0.25Mn_0.75O₃ phase, the YNi_0.50Mn_0.50O₃ compound exhibits a magnetic transition at The magnetic structure consists of two collinear Mn⁴⁺ and Ni²⁺ ferromagnetic layers (F_x0F_z magnetic configurations) with saturated magnetic moment values of 2.25(2) and 1.57(2) μ_B for Mn⁴⁺ and Ni²⁺, respectively, at 1.5 K.     

Compact diode-side-pumped Nd:YVO<Subscript>4</Subscript> laser in grazing-incidence configuration

The analysis of compact CW diode-side-pumped grazing-incidence-geometry Nd:YVO₄ laser designs is presented. An output power of 5 W (λ=1064 nm) was produced at 17 W of diode pump (conversion efficiency of 30%) in single transverse TEM₀₀ mode operation at high laser beam quality (M_x ²≈1.05 and M_y ²≈1.01). The resonator geometry was analyzed by applying generalized 4×4 matrix modeling of the spatial mode size, including the impact on the laser operation of cavity astigmatism and a thermal lens in the laser slab. The simplicity and compactness of the laser cavities allow their use for technological applications. Received: 31 July 2002 / Published online: 22 January 2003 RID="*" ID="*"Corresponding author. Fax: +44-20/7594-7744, E-mail: m.damzen@ic.ac.uk     

Countercomplementarity and strong ferromagnetic coupling in a linear mixed mu-acetato, mu-hydroxo trinuclear copper(II) complex. Synthesis, structure, magnetic properties, EPR, and theoretical studies

The structural and magnetic data of the trinuclear compound [Cu3(L)2(CH3COO)2(OH)2(dmf)2] (HL = N-(2-methylpyridyl)toluensulfonylamide) are reported. The compound crystallizes in the monoclinic system, space group P2(1)/n (no. 14), with a = 11.6482(6) A, b = 13.5772(6) A, c = 13.5306(7) A, alpha = 90 degrees, beta = 92.859(5) degrees, gamma = 90 degrees, and Z = 2. The three copper atoms form an exact linear arrangement. Neighboring coppers are connected by a hydroxo bridge and a bidentate syn-syn carboxylato group. The coordination spheres of the terminal copper atoms are square pyramidal with a dmf molecule as the apical ligand. The central copper has a regular square planar geometry. The mixed bridging by a hydroxide oxygen atom and a bidentate carboxylato group leads to a noncoplanarity of the adjacent basal coordination planes with a dihedral angle of 51.96(9) degrees. Susceptibility measurements (2-300 K) reveal a strong ferromagnetic coupling, J = 93(6) cm-1, in the mixed-bridged moiety leading to a quartet ground state that is confirmed by the EPR spectra. The ferromagnetic exchange coupling is discussed using DFT calculations on model compounds that have shown a countercomplementary effect of the hydroxo and acetate bridges.