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33 results on '"Atria, A. M."'

17. Redox, kinetics, and complexation chemistry of the CrVI/CrV/CrIV -D-glycero-D-gulo-heptono-1,4-lactone System.

Author

Mangiameli, María F., González, Juan C., García, Silvia, Bellú, Sebastián, Santoro, Mabel, Caffaratti, Evangelina, Frascaroli, María I., Peregrín, Juan Manuel Salas, Atria, Ana M., and Sala, Luis F.

Subjects
OXIDATION-reduction reaction, CHEMICAL kinetics, CHROMIUM compounds, LACTONES, CHEMICAL reactions, FORMIC acid, INTERMEDIATES (Chemistry)
Abstract

When a 60-times or higher excess of D-glycero-D-gulo-heptono-1,4-lactone (GHL) over CrVI is used, reaction yields D-gluconic acid, formic acid and CrIII as final products. The redox reaction involves formation of intermediates, CrIV and CrV species, reacting with GHL at comparable rates. CrIV is a very reactive intermediate and does not accumulate during this reaction; its rate of disappearance is 2.0 × 104 and 4.0 × 103 times higher than CrVI or CrV reaction with GHL, respectively. Kinetic studies show that the redox reaction proceeds through a mechanism combining CrVI → CrIV → CrII and CrVI → CrIV → CrIII pathways. This mechanism is supported by the observation of free radicals, superoxoCrIII (CrO22+) and oxo-CrV as intermediates species. Complete rate laws for the GHL/chromium redox reaction are described in the present work. EPR spectra show that five-coordinate oxo-CrV bischelates (giso1 = 1.9802; giso2 = 1.9803) are formed at pH ≤ 4 where the OH and O-ring groups of GHL participate in the bonding to oxo-CrV. Penta-coordinated oxo-CrV monochelates are observed as minor species (giso3 = 1.9866; giso4 = 1.9879) in addition to the major penta-coordinated oxo-CrV bischelates. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2010
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23. Redox and complexation chemistry of the CrVI/CrV–d-galacturonic acid system

Author

González, Juan C., Daier, Verónica, García, Silvia, Goodman, Bernard A., Atria, Ana M., Sala, Luis F., and Signorella, Sandra

Abstract

The oxidation of d-galacturonic acid by CrVI yields the aldaric acid and CrIII as final products when a 30-times or higher excess of the uronic acid over CrVI is used. The redox reaction involves the formation of intermediate CrIV and CrV species, with CrVI and the two intermediate species reacting with galacturonic acid at comparable rates. The rate of disappearance of CrVI, CrIV and CrV depends on pH and [substrate], and the slow reaction step of the CrVI to CrIII conversion depends on the reaction conditions. The EPR spectra show that five-coordinate oxo–CrV bischelates are formed at pH ≤ 5 with the uronic acid bound to CrV through the carboxylate and the α-OH group of the furanose form or the ring oxygen of the pyranose form. Six-coordinated oxo–CrV monochelates are observed as minor species in addition to the major five-coordinated oxo–CrV bischelates only for galacturonic acid ∶ CrVI ratio ≤ 10 ∶ 1, in 0.25–0.50 M HClO4. At pH 7.5 the EPR spectra show the formation of a CrV complex where the vic-diol groups of Galur participate in the bonding to CrV. At pH 3–5 the Galur–CrV species grow and decay over short periods in a similar way to that observed for [Cr(O)(α-hydroxy acid)2]−. The lack of chelation at any vic-diolate group of Galur when pH ≤ 5 differentiates its ability to stabilise CrV from that of neutral saccharides that form very stable oxo–CrV(diolato)2 species at pH > 1.

Published
2004

24. Magneto-structural characterization of Cu4(prz)2(L)2Cl4 ·CH3CH2OH (LH=1,1-di-2-pyridyl-1-ethoxi methanol, przH=pyrazole)

Author

Baggio, R., González, O., Garland, M. T., Manzur, J., Acuña, V., Atria, A. M., Spodine, E., and Peña, O.

Abstract

The title compound, Cu2C17H16O2.5Cl2, is a copper(II) complex, in which each dimeric unit has two copper atoms bridged by a pyrazolato ligand, a di(2-pyridyl)]methane ligand, and an oxygen atom from the modified methylene group that links the two pyridine rings (O-C-O-CH2CH3). The complex crystallizes in the monoclinic groupP21/n,a=7.7330(1),b=19.589(6),c=13.123(2)Å,ß=95.020(0)°,V=1980.3(7)Å3,Z=4,Fw=514.3,DDo=1.725 g cm-3?(MoKa)=0.71073 Å,F(000)=1032,µ=2.44 mm-1, R=0.044 for 2209 observed reflections,Rw=0.047,s=0.086. Each dimer is linked to the next unit by long chlorine bonds (Cu(2')-Cl(1)=2.846(2)Å). These tetrameric units form zigzagged chains through copperchlorine bonds of 3.380(2)Å. The copper(II) complex presents antiferromagnetic behavior withTm=161 K.

Published
1993
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