Showing papers by "Enrique J. Baran published in 2011"

Synthesis and Characterization of Heteroleptic Copper and Zinc Complexes with Saccharinate and Aminoacids. Evaluation of SOD-like Activity of the Copper Complexes

Abstract: Five new copper and zinc heteroleptic complexes with saccharin and aminoacids with general stoichiometry Na(2)[M(sac)(2)(aa)(2)].nH(2)O (M denotes Cu or Zn, sac the saccharinate ion, and aa the aminoacids) were synthesized and characterized by elemental and thermogravimetric analysis, conductimetric measurements and IR, Raman and UV-vis spectroscopies. In all the complexes, copper and zinc ions coordinated with the aminoacids through the terminal amine and carboxylate residues and with saccharin through the heterocyclic nitrogen atom. Besides, the superoxide dismutase-like activity of the heteroleptic copper complexes was evaluated and compared with the homoleptic copper amino acid complexes with the aim to observe the influence of the saccharin coordination.

Synthesis and characterization of Ca2CoTaO6, a new monoclinically distorted double perovskite

Abstract: The new Ca2CoTaO6 double perovskite has been synthesized by a conventional solid state reaction and its unit cell parameters determined by X-ray powder diffractometry. It crystallizes in the monoclinic space group P21/n. The unit cell parameters are: a = 5.507(2) A; b = 5.564(3) A; c = 7.798(3) A; β = 89.99(4)° and Z = 2. The IR spectrum of the material was recorded and is briefly discussed. Some comparisons with Ca2CoNbO6 and other isostructural perovskites are also performed.

The dehydration of SrTeO3(H2O)--a topotactic reaction for preparation of the new metastable strontium oxotellurate(IV) phase ε-SrTeO3.

Abstract: Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO3(H2O), was obtained by microwave-assisted hydrothermal synthesis under alkaline conditions at 180 °C for 30 min. A temperature of 220 °C and longer reaction times led to single crystal growth of this material. The crystal structure of SrTeO3(H2O) was determined from single crystal X-ray diffraction data: P21/c, Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5) A, β = 107.210(1)°, V = 443.42(5) A3, 1403 structure factors, 63 parameters, R[F2>2σ(F2)] = 0.0208, wR(F2 all) = 0.0516, S = 1.031. SrTeO3(H2O) is isotypic with the homologous BaTeO3(H2O) and is characterised by a layered assembly parallel to (100) of edge-sharing [SrO6(H2O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO3] units. The cohesion of the structure is accomplished by moderate O–H⋯O hydrogen bonding interactions between donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction, SrTeO3(H2O) condensates above 150 °C to the metastable phase e-SrTeO3 and transforms upon further heating to δ-SrTeO3. The crystal structure of e-SrTeO3, the fifth known polymorph of this composition, was determined from combined electron microscopy and laboratory X-ray powder diffraction studies: P21/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2) A, β = 126.4980(7)°, V = 341.20(18) A3, RFobs = 0.0166, RBobs = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of e-SrTeO3 shows the same basic set-up as SrTeO3(H2O), but the layered arrangement of the hydrous phase transforms into a framework structure after elimination of water. The structural studies of SrTeO3(H2O) and e-SrTeO3 are complemented by thermal analysis and vibrational spectroscopic measurements.

Synthesis and characterization of bistropolonato oxovanadium(IV and V) complexes

Abstract: Oxovanadium(IV) and oxovanadium(V) complexes of tropolone (Htrp, 2-hydroxy-2,4,6-cycloheptatrien-1-one), of stoichiometry VO(trp)2 and VO(trp)2Cl, were characterized by electronic, infrared, and Raman spectroscopies. Their electrochemical behavior was investigated by cyclic voltamperommetry in dimethylsulfoxide solutions. The magnetic susceptibility of VO(trp)2 was investigated between 2 and 300 K. The vibrational spectra of the related Co(trp)2, Cu(trp)2, and Zn(trp)2 complexes were also analyzed for comparative purposes.

VIBRATIONAL SPECTRA OF THE α-M II C 2 O 4 ⋅2H 2 O OXALATO COMPLEXES, WITH M II = Co, Ni, Zn

Abstract: The infrared and Raman spectra of the α-M II C2O4⋅2H2O oxalate complexes with M II = Co, Ni and Zn were recorded and briefly discussed on the basis of their structural peculiarities. The IR spectrum of a partially deuterated sample of α-ZnC2O4⋅2H2O is also discussed, reinforcing some of the performed assignments in the lower energy spectral region.

Crystal and Molecular Structure of a New Hydroxylamido/Amino Acid Oxovanadium(V) Complex, [VO(NH2O)2(DL-methioninato)]·H2O

Abstract: The crystal and molecular structure of the [VO(DLmeth)( NH2O)2]・H2O complex has been determined by X-ray diffraction methods (monoclinic, P21/c with a = 5.8138(2), b = 27.3496(8), c = 7.5663(2) A° , β = 103.059(3)◦, and Z = 4). The vanadium(V) cation is in a pentagonal bipyramidal environment axially coordinated to the oxo group and equatorially to two hydroxylamido groups in a side-on fashion. The fifth equatorial binding site and the other apical position are occupied by an N and an O atom, respectively, from the methioninate anion acting as a bidentate ligand. Graphical Abstract Crystal and Molecular Structure of a New Hydroxylamido/Amino Acid Oxovanadium(V) Complex, [VO(NH2O)2(DL-methioninato)]·H2O