Showing papers by "Enrique J. Baran published in 2002"
TL;DR: These studies clearly demonstrated that members from the main traditional subfamilies of the Cactaceae family could synthesize different chemical forms of calcium oxalate, suggesting a definite but different genetic control.
Abstract: The chemical composition and morphology of solid material isolated from various Cactaceae species have been analyzed. All of the tested specimens deposited high-purity calcium oxalate crystals in their succulent modified stems. These deposits occurred most frequently as round-shaped druses that sometimes coexist with abundant crystal sand in the tissue. The biominerals were identified either as CaC2O4.2H2O (weddellite) or as CaC2O4.H2O (whewellite). Seven different species from the Opuntioideae subfamily showed the presence of whewellite, and an equal number of species from the Cereoideae subfamily showed the deposition of weddellite. The chemical nature of these deposits was assessed by infrared spectroscopy. The crystal morphology of the crystals was visualized by both conventional light and scanning electron microscopy. Weddellite druses were made up of tetragonal crystallites, whereas those from whewellite were most often recognized by their acute points and general star-like shape. These studies clearly demonstrated that members from the main traditional subfamilies of the Cactaceae family could synthesize different chemical forms of calcium oxalate, suggesting a definite but different genetic control. The direct relationship established between a given Cactaceae species and a definite calcium oxalate biomineral seems to be a useful tool for plant identification and chemotaxonomy.
145 citations
TL;DR: Three new copper(II) complexes of stoichiometry [Cu(L-dipeptide)].nH(2)O, containing as ligands the dipeptides L-alanine-L-isoleucine, L-Alanine- L-threonine and L-al-tyrosine were prepared and characterized by single crystal X-ray diffractometry, and electronic and infrared spectroscopy.
52 citations
TL;DR: The synthesis of the new complex [Re(III)(N-allylthiourea)6](PF6)3 is reported, and information about its structural characteristics was obtained comparing its IR spectrum with those of the other complexes of the investigated series.
39 citations
TL;DR: In this paper, the synthesis of two heterobimetallic EDTA complexes, MgCu(EDTA) and ZnCu(6H2O), was described by means of vibrational (infrared and Raman) and electronic spectroscopy.
Abstract: The synthesis of two heterobimetallic EDTA complexes, MgCu(EDTA).6H2O and ZnCu(EDTA).6H2O, is described. They were characterized by means of vibrational (infrared and Raman) and electronic (reflectance) spectroscopy. Several dissolution tests in 0.1 N HCl and simulated gastric juice were also performed. The results support the potential usefulness of these complexes for copper supplementation in human and veterinary medicine and to the simultaneous reinforcement of Mg(II) and Zn(II) levels.
32 citations
24 citations
TL;DR: In this article, a rationalization of the conspicuous different abilities of saccharin and thiosaccharin to form coordination compounds with the first series of transition metal elements and to interact with heavy metal cations is sought.
Abstract: A rationalization of the conspicuous different abilities of saccharin and thiosaccharin to form coordination compounds with the first series of transition metal elements and to interact with heavy metal cations is sought.Their electronic molecular structures as well as those of their respective ions are compared performing natural bond orbitals (NBO) analyses of the four species. Upon deprotonation, the negative charge at the N atom in saccharin is almost constant while it decreases in thiosaccharin and the negative charge at the monocoordinated chalcogen atom is notably more increased in the latter than in the former. Apparently, the negative charge reorganization makes difficult the coordination of thiosaccharin with the first series of transition metal elements and favors its experimentally observed interaction with heavy metal cations such as cadmium, lead, mercury, silver, and thallium.
22 citations
21 citations
14 citations
TL;DR: In this paper, the crystal structure of the title complex has been determined by single X-ray diffraction methods and refined to an R-value of 0.0543, which represents only the second known example of a simple mononuclear metal complex containing simultaneously N-and O-bonded saccharinato ligands.
Abstract: The crystal structure of the title complex has been determined by single X-ray diffraction methods and refined to an R-value of 0.0543. It crystallizes in the monoclinic P2 1 /a space group with a = 21.1231(9), b = 9.4523(4), c = 16.1874(7) A, β = 107.3706(3)° and Z = 4. The compound represents only the second known example of a simple mononuclear metal complex containing simultaneously N- and O-bonded saccharinato ligands. Its infrared spectrum and thermal behavior are also briefly discussed.
13 citations
TL;DR: The crystal structures of [M(nic) 2 (H 2 O) 4 ](sac) 2 with Co(II), Ni(II, and Zn(II) were determined at 116 K by single-crystal X-ray diffractometry as mentioned in this paper.
Abstract: The crystal structures of [M(nic) 2 (H 2 O) 4 ](sac) 2 (nic = nocotinamide; sac = saccharinate anion) with M = Co(II), Ni(II) and Zn(II), have been determined at 116 K by single-crystal X-ray diffractometry. The compounds crystallize in the triclinic space group P1 with Z = 1, and the M(II) cations present a slightly distorted MN 2 O 4 octahedral environment, with equatorially coordinated water molecules and axially pyridine N-bound nicotinamide ligands. The saccharinate anions act as counteranions, and are not part of the first coordination sphere. Some comparisons with related structures have been made and the most important features of their IR spectra discussed.
11 citations
01 Jan 2002
TL;DR: In this article, the infrared and Raman spectra of the Bis(L-metioninato)cobre(II) complex were recorded and briefly discussed on the basis of its structural characteristics.
Abstract: SUMMARY. The infrared and Raman spectra of the tittle complex were recorded and briefly discussed on the basis of its structural characteristics. Some comparisons with related Cu(II)/amino acid complexes were made. RESUMEN. “Espectro Vibracional del Bis(L-metioninato)cobre(II)”. Se registraron los espectros de infrarojo y Raman del complejo del titulo y se los discutio brevemente en base a sus carcateristicas estructurales. Se hacen algunas comparaciones con otros complejos de Cu(II)/amino acidos relacionados.
Abstract: The crystal structure of [Cu(sac) 2 (nic) 2 (H 2 O)] (sac = saccharinate anion; nic = nicotinamide) has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/c with Z = 4 and the Cu(II) ion presents a CuN 4 O square pyramidal coordination. Some comparisons with related structures are made and the most important features of its IR spectrum were also discussed.
01 Jan 2002
TL;DR: In this article, the infrared spectrum of the Ag(NH2C6H4COO) complex was recorded and briefly discussed in relation to its structural characteristics, and the solubility of the compound in water, at 20 °C, was determined by conductimetric measurements.
Abstract: The infrared spectrum of the Ag(NH2C6H4COO) complex was recorded and briefly discussed in relation to its structural characteristics. The solubility of the compound in water, at 20 °C, was determined by conductimetric measurements. For comparative purposes similar measurements were also performed with the Ag(I) complexes of saccharin and sulfadiazine. The results suggest that the anthranilate and saccharinate complexes may be useful as slow silver releasing systems in pharmaceutical formulations. RESUMEN. “Caracterizacion de antranilato de plata, un promisorio agente antibactericida”. Se registro el espectro de infrarrojo del complejo Ag(NH2C6H4COO) y se lo discutio brevemente en base a sus caracteristicas estructurales. La solubilidad del compuesto en agua, a 20 °C, se determino mediante medidas conductimetricas. Con fines comparativos se realizaron mediciones similares con los complejos que la Ag(I) forma con la sacarina y la sulfadiazina. Los resultados sugieren que los complejos de antranilato y de sacarinato podrian ser utiles como sistemas de liberacion lenta de plata en formulaciones farmaceuticas.
TL;DR: In an attempt to obtain new square grid polymers we could prepare the copper(II) complex [Cu(4, 4'-bipy)2 (H2O)2 ] by single crystal X-ray diffraction methods as mentioned in this paper, which is a square grid polymer with the saccharinate anions sandwiched between the complex layers and the DMF molecules filling the square holes.
Abstract: In an attempt to obtain new square grid polymers we could prepare the copper(II) complex [Cu(4, 4'-bipy)2 (H2O)2](sac)2 · DMF (4, 4'-bipy = 4, 4'-bipyridine; sac = anion of saccharin; DMF = dimethylformamide) Its structure was determined by single crystal X-ray diffraction methods It crystallizes in the orthorhombic space group Pcnb (a = 144994(2), b = 158128(3), c = 166850(2) A, Z = 4) and is a square grid polymer with the saccharinate anions sandwiched between the complex layers and the DMF molecules filling the square holes UV-vis, diffuse reflectance and IR spectra, room temperature magnetic susceptibility and the thermal behaviour were also investigated
Charakterisierung eines neuartigen, viereckige Gitter enthaltenden CuII/4, 4'-Bipyridin Koordinationspolymer
Bei Versuchen neue viereckige Gitter-Polymere zu erhalten, gelang es den Kupfer(II)-Komplex [Cu(4, 4'-bipy)2(H2O)2] (sac)2 · DMF (4, 4'-bipy = 4, 4'-Bipyridin; sac = Anion des Saccharins; DMF = Dimethylformamid) darzustellen Seine Struktur wurde rontgenographisch an Einkristallen bestimmt Er kristallisiert in der orthorhombischen Raumgruppe Pcnb (a = 144994(2), b = 158128(3), c = 166850(2) A, Z = 4) und bildet ein viereckiges Polymer-Gitter mit den Saccharinat-Anionen zwischen den Komplex-Schichten und mit den DMF-Molekulen in viereckigen Lucken UV-vis-, Reflexions- und IR-Spektren, sowie die magnetische Suszeptibilitat (bei Raumtemperatur) und das thermische Verhalten, wurden auch untersucht
TL;DR: In this article, the infrared and Raman spectra of YbBiGeO5 were recorded and briefly discussed on the basis of its structural peculiarities, and some comparisons with related species are made.
Abstract: The infrared and Raman spectra of YbBiGeO5 were recorded and are briefly discussed on the basis of its structural peculiarities. The infrared spectra of the complete series of isostructural LnBiGeO5 compounds (Ln = Dy–Lu and Y) were also recorded and some comparisons with related species are made. Copyright © 2002 John Wiley & Sons, Ltd.
TL;DR: In this paper, the electrochemical behavior of Co(creatinine)2Cl2 was investigated by cyclic voltammetry in organic solvents (DMSO and DMF) and in aqueous solution.
Abstract: The electrochemical behavior of Co(creatinine)2Cl2 was investigated by cyclic voltammetry in organic solvents (DMSO and DMF) and in aqueous solution. Analysis of the results indicates that the electroactive species depend on the nature of the solvent. In DMF a single reduction process Co(II)/Co(I) is observed. In DMSO the redox behavior of the complex changes with the scan rate and a two-electron transfer process can be eventually observed. In aqueous solution the complex immediately decomposes giving rise to the aquo-cation. The characteristic peak of the redox couple Cl2/Cl− is observed as a consequence of the chloride released from the coordination sphere. Analysis of the electronic spectra gave additional support to the proposed mechanisms. The Co-Cl and Co-N stretching bands were clearly identified in the low frequency region of the IR spectrum.
TL;DR: In this article, the least squares computer program letagrop was applied to the experimental emf and UV-Vis data, taking into account the hydrolytic species of VO 2+ ion.
TL;DR: In this article, the complex [ReO(Me4tu)4]3+, with Me4tu = tetramethylthiourea, was characterized in nonaqueous media.
Abstract: The complex [ReO(Me4tu)4]3+, with Me4tu = tetramethylthiourea, is characterized in nonaqueous media. Its structure is studied in acetonitrile solution by 1H and 13C NMR and its electrochemical behavior in the same solvent is analyzed by means of cyclic voltamperometric measurements. Heteronuclear correlation and variable temperature NMR experiments suggest that the complex ion shows a similar structure in solution and in the solid state. At low temperatures (below 0°C) free rotation of the dimethylamine groups around the thiocarbonyl carbon-nitrogen bond is restricted and the dissolved complex adopts the rigid structure observed in the solid state. Cyclic voltamperometric results suggest that the redox behavior of this compound can be explained through an ErCiEr mechanism (a chemical reaction coupled between two electron-transfer reactions). An initial one electron reduction of the complex from Re(V) to Re(IV) followed by an irreversible chemical reaction, leads to a new electroactive species of Re(IV)*, ...
TL;DR: The molecular structure of diosgenone, a natural steroidal sapogenin and isolated from Solanum nudum, was solved by single crystal X-ray diffractometry at 120 K and refined by full-matrix least-squares to an agreement factor, R1 = 0.054.
Abstract: The molecular structure of diosgenone, a natural steroidal sapogenin, closely related to diosgenin and isolated from Solanum nudum, was solved by single crystal X-ray diffractometry at 120 K and refined by full-matrix least-squares to an agreement factor, R1 = 0.054. It crystallizes in the monoclinic space group P2(1), with a = 15.1870(4) A, b = 7.2710(2) A, c = 21.2840(6) A, beta = 99.251(1) degrees, and four molecules in the unit cell (Z = 4). The results constitute the first structural report on a steroidal sapogenin from the diosgenin group.
TL;DR: In this article, the FT-infrared spectra of Ca 2 CuO 2 Cl 2, Ca 2 Co 2 O 2 Br 2, and Sr 2 Co O 2 Cl Cl 2 were discussed on the basis of their structural characteristics and in comparison with the spectras of related materials.
TL;DR: In this paper, the authors present a survey of the state-of-the-art performance of the current state of the art on the following metrics: 100 0.0357 0.047 0.0536 0.052 0.072 0.061 0.
Abstract: 0 0.0357 0.0443 0.0477 0.046 0.061 100 0.0357 0.0443 0.0478 0.046 0.061 200 0.0357 0.0446 0.0486 0.047 0.063 298.16 0.0359 0.0459 0.0509 0.049 0.067 300 0.0359 0.0459 0.0509 0.049 0.067 400 0.0363 0.0481 0.0542 0.052 0.073 500 0.0370 0.0508 0.0579 0.055 0.078 600 0.0380 0.0536 0.0616 0.059 0.084 700 0.0391 0.0566 0.0654 0.062 0.090 800 0.0403 0.0595 0.0691 0.066 0.095 900 0.0417 0.0624 0.0726 0.069 0.100 1000 0.0430 0.0652 0.0760 0.072 0.105
TL;DR: In this article, a superexchange mechanism for polycrystalline R 2 Ba 2 CuPtO 8 (R =Ho, Er, Tm, Yb, Lu and Y) oxides has been proposed in which the Cu 2+ sublattice plays an important role as promoter of the antiferromagnetic interactions of ferromagnetic R 3+ coupled in the a-c plane of the structure.