Elizabeth Chacón Villalba - Academia.edu (original) (raw)
Papers by Elizabeth Chacón Villalba
Inorganica Chimica Acta, 2013
Three new 1D and 2D coordination polymers, {(pipH 2)[Ce 2 (tda) 4 (H 2 O) 2 ]. 2H 2 O} n (1), {[N... more Three new 1D and 2D coordination polymers, {(pipH 2)[Ce 2 (tda) 4 (H 2 O) 2 ]. 2H 2 O} n (1), {[Nd 2 (tda) 3 (H 2 O) 2 ].H 2 O} n (2) and {(pipH 2) [UO 2 (tda) 2 ]} n (3), where [tdaH 2 = 2,2´thiodiacetic acid and pip = piperazine] have been synthesized and characterized by elemental analysis, spectral (IR, NMR, UV-Vis and luminescence), thermal (TGA/DTA) analysis, as well as X-ray single crystal diffraction. Compounds 1 and 3 are proton transfer salts of the piperazindiium cation and metal complex anions that crystallized in a solution from dicarboxylic acid, piperazine and metal nitrates or acetates as starting materials. However compound 2 is an interesting neutral 2D coordination polymer containing just 2,2´thiodiacetate dianions. The acid is coordinated to metal center in a bidentate fashion in 2 and 3 while in 1, coordinated to metal center as bidentate and tridentate, simultaneously. The coordination polyhedron around metal center in 1, 2 and 3 can be described as distorted
Reactive and Functional Polymers, 2014
Congo Red (CR) is a hydrophobic dye commonly used for diagnosis and potentially useful as therape... more Congo Red (CR) is a hydrophobic dye commonly used for diagnosis and potentially useful as therapeutic agent of beta amyloid plaques in neurodegenerative diseases. CR, as drug model, was encapsulated on Alginate-Carboxy Methyl Guar Gum (Alg-CMGG) blend microspheres. Guar gum 18% carboxymethylated (CMGG) derivative was synthesized in order to improve aqueous solubility, polymer blending and help reduce surface tension. The derivative was confirmed by FTIR spectroscopy, and elemental analysis. Surface tension of the new CMGG is reduced in about 50% compared with the native polymer. Lowering of Guar Gum (GG) aqueous solutions viscosity from 30,000 cps to 350-400 cps in case of CMGG is indicating pseudoplastic fluid behavior modifications. Vibrational spectroscopy analysis confirmed interactions among CR molecules in alginate-CMGG matrices ascribed largely to the aromatic motif of the dye and the biopolymer a polar regions. CR was encapsulated on 68/32% alginate/CMGG blend microspheres as the best formulation tested. The release of CR from the microspheres was not detected at pH = 1.2 in 25 min, but 62% of CR was found in the supernatant when the pH was raised to 7.4 at 37°C after 8 h incubation.
Reactive and Functional Polymers, 2016
Six pectins with 35% to 91% methoxylation degree were purified and characterized to encapsulate C... more Six pectins with 35% to 91% methoxylation degree were purified and characterized to encapsulate Crystal Violet (CV). Amidated low methoxylated pectin (ALMP) was selected based on microsphere morphologies, aqueous solubility, viscosity and the effect of calcium concentration. Pectin microspheres were stabilized with Arabic gum (AG) and optimized according to the loading. Microspheres composed of 2.0% ALMP-1.0% AG crosslinked with 450 mM calcium(II) were able to encapsulate 217 ± 2 μM CV. Optical microscopy of the gels revealed spheroid microspheres with 250 ± 50 μm diameter containing homogenous CV distribution. Dried microspheres observed by SEM and epifluorescence showed a highly shrinkable matrix keeping the spheroidal morphology. Low relative viscosity of the ALMP-AG-CV solutions was found compared to ALMP and ALMP-AG. The Young moduli (60-80 Pa) of ALMP-AG microspheres by texturometric analysis indicated that the CV could interfere with the gel crosslinking. Raman spectroscopy analysis suggested some interaction of CV nucleophilic center within the matrix. FTIR of the matrix showed largest shifts in the carbonyl and carboxylate groups probably associated to H-bridges. CV stability studies performed on ALMP-AG microspheres, synthetized from polymer solutions with pH values above and below pectin pKa and showed faster CV release rates in presence of ionic strength.
VI Jornadas de Investigación, Transferencia, Extensión y Enseñanza (ITEE) (La Plata, 14 al 16 de septiembre de 2021), 2021
Please cite this article as: M. Elizabeth Chacón Villalba, Carlos A. Franca, Jorge A. Güida , Pho... more Please cite this article as: M. Elizabeth Chacón Villalba, Carlos A. Franca, Jorge A. Güida , Photo release of nitrous oxide from the hyponitrite ion studied by infrared spectroscopy. Evidence for the generation of a cobalt-N2O complex. Experimental and DFT calculations. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Saa(2017), doi: 10.1016/j.saa.2017.01.003
Uno de los tipos de complejos más estudiados en los laboratorios del Programa QUINOR es el de los... more Uno de los tipos de complejos más estudiados en los laboratorios del Programa QUINOR es el de los aniones pentacianonitrosilmetalato, asociados con diversos cationes. En el presente trabajo se abordó el más conocido de ellos: el pentacianonitrosilferrato(2-), comúnmente denominado nitroprusiato, en forma de la sal sódica dihidratada, Na2[Fe(CN)5NO].2H2O. El presente trabajo tuvo, precisamente, como finalidad, confirmar asignaciones y desplazamientos isotópicos y aprovecharlos para tratar de refinar el campo de fuerzas. Para ello se ha reunido información espectroscópica IR y Raman, entre 4000 y 50 cm-1, tanto de la especie isotópicamente normal (de composición isotópica natural) como enriquecida en diferentes grados con 54Fe, 13C y 15N (en el grupo NO), información que se ha empleado para desarrollar un campo de fuerzas mejorado mediante el uso de programas de cálculo adecuados. Además de reunir la información necesaria para realizar los cálculos anteriormente mencionados, también a...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017
The solid state photolysis of sodium, silver and thallium hyponitrite (M 2 N 2 O 2 , M = Na, Ag, ... more The solid state photolysis of sodium, silver and thallium hyponitrite (M 2 N 2 O 2 , M = Na, Ag, Tl) salts and a binuclear complex of cobalt bridged by hyponitrite ([Co(NH 3) 5-N(O)-NO-Co(NH 3) 5 ] 4+) were studied by irradiation with visible and UV light in the electronic absorption region. The UV-visible spectra for free hyponitrite ion and binuclear complex of cobalt were interpreted in terms of Density Functional Theory calculations in order to explain photolysis behavior. The photolysis of each compound depends selectively on the irradiation wavelength. Irradiation with 340-460 nm light and with the 488 nm laser line generates photolysis only in silver and thallium hyponitrite salts, while 253.7 nm light photolyzed all the studied compounds. Infrared spectroscopy was used to follow the photolysis process and to identify the generated products. Remarkably, gaseous N 2 O was detected after photolysis in the infrared spectra of sodium, silver, and thallium hyponitrite KBr pellets. The spectra for [Co(NH 3) 5-N(O)-NO-Co(NH 3) 5 ] 4+ suggest that one cobalt ion remains bonded to N 2 O from which the generation of a [(NH 3) 5 CoNNO] +3 complex is inferred. Density Functional Theory (DFT) based calculations confirm the stability of this last complex and provide the theoretical data which are used in the interpretation of the electronic spectra of the hyponitrite ion and the cobalt binuclear complex and thus in the elucidation of their photolysis behavior. Carbonate ion is also detected after photolysis in all studied compounds, presumably due to the reaction of atmospheric CO 2 with the microcrystal surface reaction products. Kinetic measurements for the photolysis of the binuclear complex suggest a first order law for the intensity decay of the hyponitrite IR bands and for the intensity increase in the N 2 O generation. Predicted and experimental data are in very good agreement.
Acta Crystallographica Section A Foundations of Crystallography, 2009
Page s 250 transition metal elements TM = E8-E10. In the system Ba-Ni-Ge, two homogeneity ranges ... more Page s 250 transition metal elements TM = E8-E10. In the system Ba-Ni-Ge, two homogeneity ranges with different Ni content are structurally characterized, which are both related to the clathrate-I structure. Compounds with low Ni content, Ba 8 Ni x Ge 42±1 (0 < x ≤ 0.6), can be considered as solution of Ni in the binary Ba 8 Ge 43 3 (space group Ia-3d, a = 21.307(2) Å). The subcell with space group Pm-3n is observed for the compositions Ba 8 Ni x Ge 42±1 (0.6 < x ≤ 4.2). The change in Ni content is associated with the respective change in lattice parameters (a = 10.657(1)-10.681(1) Å), but also confirmed by microprobe analyses.
![Research paper thumbnail of Infrared and Raman spectra of -thallium nitroprusside, Tl2[Fe(CN)5NO]](https://attachments.academia-assets.com/86652575/thumbnails/1.jpg)
](Vibrational Spectroscopy, 2000
Ž w Ž. x. Interferometric infrared and Raman spectra of thallium nitroprusside Tl Fe CN NO , with... more Ž w Ž. x. Interferometric infrared and Raman spectra of thallium nitroprusside Tl Fe CN NO , with normal isotopic composi-2 5 13 Ž. y1 Ž. tion or substituted with C 98.5% , were obtained from 4000 to 50 cm at room and low temperature boiling liquid air. Infrared microscopy used with selected monocrystals allowed the detection of very weak overtone and combination bands. Comparisons are made with other nitroprusside salts, anhydrous and hydrated, and especially with sodium nitroprusside dihydrate.
Vibrational Spectroscopy, 1997
... [8]. ME Chacón Villalba. In: (72nd ed.),Doctoral Thesis, Facultad de Ciencias Exactas, Univer... more ... [8]. ME Chacón Villalba. In: (72nd ed.),Doctoral Thesis, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, R. Argentina (1995). [9]. ME Chacón Villalba, EL Varetti, PJ Aymonino, Part II, submitted for publication. [10]. R. Marqués. In: (72nd ed.),Rep. No. ...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2001
Infrared spectra of the metastable state I (MSI) of normal and 15NO, N18O and 54Fe isotopically s... more Infrared spectra of the metastable state I (MSI) of normal and 15NO, N18O and 54Fe isotopically substituted sodium nitroprusside dihydrate (Na2[Fe(CN)5NO].2H2O) have been obtained at 77 K. A comparison of the isotopic shifts measured for the vibrational modes of the FeXY (XY = NO or ON) moiety with those calculated by means of quantum chemistry (DFT) procedures supports the linear Fe-O = N arrangement for the MSI state.
![Research paper thumbnail of Crystal and molecular structure and photoisomerization of nitropentaamminecobalt(III) nitroprusside sesquihydrate, [Co(NH3)5NO2][Fe(CN)5NO]·1.5H2O](https://attachments.academia-assets.com/86652565/thumbnails/1.jpg)
](Polyhedron, 2002
The crystal structure of nitropentaamminecobalt(III) nitroprusside sesquihydrate, [Co(NH 3) 5 NO ... more The crystal structure of nitropentaamminecobalt(III) nitroprusside sesquihydrate, [Co(NH 3) 5 NO 2 ][Fe(CN) 5 NO] ×/1.5H 2 O has been determined by Patterson and Fourier methods employing 3881 independent X-ray reflections with I /2s (I) and refined by full-matrix least-squares to R 1 0/0.032. The substance crystallizes in the monoclinic C 2/c (C 2h 6) space group No. 15, with a 0/ 28.408(3), b 0/6.422(1), c 0/22.401(3) Å , b 0/123.55(1)8 and Z0/8. The metastable state I (MSI) of the nitroprusside anion and the photochemical isomerization reaction of the nitropentaamminecobalt(III) cation to the nitrito isomer were produced by irradiation with Ar ' laser light of 488 nm wavelength at 77 K. TGA and DTA of the non-excited substance were performed under nitrogen atmosphere.
![Research paper thumbnail of Surface-enhanced Raman scattering of 4-picolylamine and its [Fe(CN)5]n− complexes](https://attachments.academia-assets.com/86652566/thumbnails/1.jpg)
](Journal of Raman Spectroscopy, 1991
Journal of Molecular Structure, 2011
4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) was purified and characterized. A new copper(II) comp... more 4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) was purified and characterized. A new copper(II) complex, [Cu(ClNbsa) 2 (NH 3) 2 ], has been prepared using the sulfonamide as ligand. The thermal behavior of both, the ligand and the Cu(II) complex, was investigated by thermogravimetric analyses (TG) and differential thermal analysis (DT), and the electronic characteristics analyzed by UV-VIS, FTIR, Raman and 1 H NMR spectroscopies. The experimental IR, Raman and UV-VIS spectra have been assigned on the basis of DFT calculations at the B3LYP level of theory using the standard (6-31 + G ⁄⁄) basis set. The geometries have been fully optimized in vacuum and in modeled dimethylsulfoxide (DMSO) solvent, using for the latter a continuum solvation model that reproduced the experimental conditions of the UV-VIS spectroscopy. The theoretical results converged to stable conformations for the free sulfonamide and for the complex, suggesting for the latter a distorted square planar geometry in both environments.
Journal of Molecular Structure, 2012
Two ligands for coordination compounds incorporating benzimidazole moieties, namely 1,1′-butane-1... more Two ligands for coordination compounds incorporating benzimidazole moieties, namely 1,1′-butane-1,4diylbis(5,6-dimethyl-1H-benzimidazole) and 1,1′-butane-1,4-diylbis(1H-benzimidazole), are synthesized and then characterized both experimentally and theoretically. Their structures are studied by single crystal X-ray diffraction, UV-Vis spectroscopy, and FT-IR spectroscopy. The optimized geometries, vibrational frequencies, vertical excitation energies of the two ligands are calculated using the (TD)DFT/B3LYP/TZVP method. The calculated results reproduce the experimental data. Additional bonding information about the coordinated N atoms in the two ligands is obtained by FMO and NBO analysis to investigate the substitutegroup effect on the coordination ability. The results confirm that the ligand with electron-donating methyl groups on the benzimidazole moieties has a stronger coordination ability.
![Research paper thumbnail of Crystal structure of tetrabutylammonium nitroprusside dihydrate, [(C4H9)4N]2[Fe(CN)5NO]·2H2O, and vibrational spectra of ground and metastable excited states of the dihydrate and the anhydrate](https://attachments.academia-assets.com/86652555/thumbnails/1.jpg)
](Journal of Chemical Crystallography - J CHEM CRYSTALLOGRAPHY, 2001
The crystal structure of tetrabutylammonium nitroprusside dihydrate (TBANPDH, [(C4H9)4N]2[Fe(CN)5... more The crystal structure of tetrabutylammonium nitroprusside dihydrate (TBANPDH, [(C4H9)4N]2[Fe(CN)5NO]·2H2O) was determined by single crystal X-ray diffraction (XRD) and the compound was also studied, as well as the anhydrous salt (TBANP), by room and low temperature Fourier Transform Infra-Red (FTIR) and room temperature Fourier Transform Near Infra-Red Raman (FTNIRR) spectroscopies. In addition to the ground states (GS), the metastable excited states (MSI and MSII) generated by laser excitation (488 nm) at low temperature were IR studied, both of the dihydrate and the anhydrate. TBANPDH crystallizes in the trigonal space group P3221, D63, with a = b = 13.777(2), c = 22.039(2) Å, and Z = 3. The structure was solved employing 1273 independent XR reflections, with I > 2s(I), by Patterson and Fourier methods and refined by full-matrix least-squares to R1 = 0.054.
Journal of Chemical Crystallography, 2007
... ME Chacón Villalba 4 EL Varetti (&) 4 PJ Aymonino Departamento de Quımica, Facultad d... more ... ME Chacón Villalba 4 EL Varetti (&) 4 PJ Aymonino Departamento de Quımica, Facultad de Ciencias Exactas, Centro de Quımica Inorgánica ... T, Al-Laham MA, Peng CY, Nanayakkara A, Gonzalez C, Challacombe M, Gill PMW, Johnson B, Chen W, Wong MW, Andres JL, Gonz ...
![Research paper thumbnail of New structural study and reinterpretation of the vibrational spectra of the μ-N,O-hyponitrite bis[pentaamminecobalt(III)]4+ cation](https://attachments.academia-assets.com/86652572/thumbnails/1.jpg)
](Inorganica Chimica Acta, 2006
The [(NH 3) 5 CoN(O)NOCo(NH 3) 5 ]Br 2 (NO 3) 2 AE 2.5H 2 O salt was studied by X-ray diffraction... more The [(NH 3) 5 CoN(O)NOCo(NH 3) 5 ]Br 2 (NO 3) 2 AE 2.5H 2 O salt was studied by X-ray diffraction methods. Such structural study confirmed the already reported binuclear, bridged structure of the complex cation and allowed a description of the main features of the lattice structure. An infrared and Raman study of that compound was also performed in order to revise the assignments of the vibrational features. Such spectroscopic study, aided by 14/15 N replacement and quantum chemistry calculations, permitted a reassignment of the spectral bands originated in the hyponitrite bridge.
Inorganic Chemistry, 2009
Lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphtoquinone) (HLap, C(15)H(14)O(3)) reacts with ... more Lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphtoquinone) (HLap, C(15)H(14)O(3)) reacts with Mn(2+) producing a novel polymeric complex with formula: [Mn(Lap)(2)](n). Two ligands chelate the metal through their ortho oxygen (O1, O2) moiety while two para oxygens, from other Lap ligands, complete the octahedral coordination sphere. Thus far, all reported Lap metal complexes are mononuclear, lack the metal-trans-quinonic (para) oxygen binding and have Lap as a bidentate ligand. Synthesis, X-ray diffraction, IR, and UV-visible spectroscopic properties, thermogravimetric analysis, and differential thermal analysis of this complex are reported along with a density functional theory study describing electron transfer from the Mn to the Lap ligand at low temperature. X-ray structure determinations at 125, 197, and 300 K describe the progressive trend of a Mn contribution to the Mn-O1 bond length as a function of T. The Mn-O1 bond distance increases with temperature and may be therefore associated with a semiquinonate action at low T by the carbonyl O1 donor (and corresponding to Mn(III)). It transforms to a more classical coordinative bond at room T and stabilizes a Mn(II) species; this is a reversible phenomenon involving Mn(II)-Mn(III) oxidation states.
Inorganica Chimica Acta, 2013
Three new 1D and 2D coordination polymers, {(pipH 2)[Ce 2 (tda) 4 (H 2 O) 2 ]. 2H 2 O} n (1), {[N... more Three new 1D and 2D coordination polymers, {(pipH 2)[Ce 2 (tda) 4 (H 2 O) 2 ]. 2H 2 O} n (1), {[Nd 2 (tda) 3 (H 2 O) 2 ].H 2 O} n (2) and {(pipH 2) [UO 2 (tda) 2 ]} n (3), where [tdaH 2 = 2,2´thiodiacetic acid and pip = piperazine] have been synthesized and characterized by elemental analysis, spectral (IR, NMR, UV-Vis and luminescence), thermal (TGA/DTA) analysis, as well as X-ray single crystal diffraction. Compounds 1 and 3 are proton transfer salts of the piperazindiium cation and metal complex anions that crystallized in a solution from dicarboxylic acid, piperazine and metal nitrates or acetates as starting materials. However compound 2 is an interesting neutral 2D coordination polymer containing just 2,2´thiodiacetate dianions. The acid is coordinated to metal center in a bidentate fashion in 2 and 3 while in 1, coordinated to metal center as bidentate and tridentate, simultaneously. The coordination polyhedron around metal center in 1, 2 and 3 can be described as distorted
Reactive and Functional Polymers, 2014
Congo Red (CR) is a hydrophobic dye commonly used for diagnosis and potentially useful as therape... more Congo Red (CR) is a hydrophobic dye commonly used for diagnosis and potentially useful as therapeutic agent of beta amyloid plaques in neurodegenerative diseases. CR, as drug model, was encapsulated on Alginate-Carboxy Methyl Guar Gum (Alg-CMGG) blend microspheres. Guar gum 18% carboxymethylated (CMGG) derivative was synthesized in order to improve aqueous solubility, polymer blending and help reduce surface tension. The derivative was confirmed by FTIR spectroscopy, and elemental analysis. Surface tension of the new CMGG is reduced in about 50% compared with the native polymer. Lowering of Guar Gum (GG) aqueous solutions viscosity from 30,000 cps to 350-400 cps in case of CMGG is indicating pseudoplastic fluid behavior modifications. Vibrational spectroscopy analysis confirmed interactions among CR molecules in alginate-CMGG matrices ascribed largely to the aromatic motif of the dye and the biopolymer a polar regions. CR was encapsulated on 68/32% alginate/CMGG blend microspheres as the best formulation tested. The release of CR from the microspheres was not detected at pH = 1.2 in 25 min, but 62% of CR was found in the supernatant when the pH was raised to 7.4 at 37°C after 8 h incubation.
Reactive and Functional Polymers, 2016
Six pectins with 35% to 91% methoxylation degree were purified and characterized to encapsulate C... more Six pectins with 35% to 91% methoxylation degree were purified and characterized to encapsulate Crystal Violet (CV). Amidated low methoxylated pectin (ALMP) was selected based on microsphere morphologies, aqueous solubility, viscosity and the effect of calcium concentration. Pectin microspheres were stabilized with Arabic gum (AG) and optimized according to the loading. Microspheres composed of 2.0% ALMP-1.0% AG crosslinked with 450 mM calcium(II) were able to encapsulate 217 ± 2 μM CV. Optical microscopy of the gels revealed spheroid microspheres with 250 ± 50 μm diameter containing homogenous CV distribution. Dried microspheres observed by SEM and epifluorescence showed a highly shrinkable matrix keeping the spheroidal morphology. Low relative viscosity of the ALMP-AG-CV solutions was found compared to ALMP and ALMP-AG. The Young moduli (60-80 Pa) of ALMP-AG microspheres by texturometric analysis indicated that the CV could interfere with the gel crosslinking. Raman spectroscopy analysis suggested some interaction of CV nucleophilic center within the matrix. FTIR of the matrix showed largest shifts in the carbonyl and carboxylate groups probably associated to H-bridges. CV stability studies performed on ALMP-AG microspheres, synthetized from polymer solutions with pH values above and below pectin pKa and showed faster CV release rates in presence of ionic strength.
VI Jornadas de Investigación, Transferencia, Extensión y Enseñanza (ITEE) (La Plata, 14 al 16 de septiembre de 2021), 2021
Please cite this article as: M. Elizabeth Chacón Villalba, Carlos A. Franca, Jorge A. Güida , Pho... more Please cite this article as: M. Elizabeth Chacón Villalba, Carlos A. Franca, Jorge A. Güida , Photo release of nitrous oxide from the hyponitrite ion studied by infrared spectroscopy. Evidence for the generation of a cobalt-N2O complex. Experimental and DFT calculations. The address for the corresponding author was captured as affiliation for all authors. Please check if appropriate. Saa(2017), doi: 10.1016/j.saa.2017.01.003
Uno de los tipos de complejos más estudiados en los laboratorios del Programa QUINOR es el de los... more Uno de los tipos de complejos más estudiados en los laboratorios del Programa QUINOR es el de los aniones pentacianonitrosilmetalato, asociados con diversos cationes. En el presente trabajo se abordó el más conocido de ellos: el pentacianonitrosilferrato(2-), comúnmente denominado nitroprusiato, en forma de la sal sódica dihidratada, Na2[Fe(CN)5NO].2H2O. El presente trabajo tuvo, precisamente, como finalidad, confirmar asignaciones y desplazamientos isotópicos y aprovecharlos para tratar de refinar el campo de fuerzas. Para ello se ha reunido información espectroscópica IR y Raman, entre 4000 y 50 cm-1, tanto de la especie isotópicamente normal (de composición isotópica natural) como enriquecida en diferentes grados con 54Fe, 13C y 15N (en el grupo NO), información que se ha empleado para desarrollar un campo de fuerzas mejorado mediante el uso de programas de cálculo adecuados. Además de reunir la información necesaria para realizar los cálculos anteriormente mencionados, también a...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2017
The solid state photolysis of sodium, silver and thallium hyponitrite (M 2 N 2 O 2 , M = Na, Ag, ... more The solid state photolysis of sodium, silver and thallium hyponitrite (M 2 N 2 O 2 , M = Na, Ag, Tl) salts and a binuclear complex of cobalt bridged by hyponitrite ([Co(NH 3) 5-N(O)-NO-Co(NH 3) 5 ] 4+) were studied by irradiation with visible and UV light in the electronic absorption region. The UV-visible spectra for free hyponitrite ion and binuclear complex of cobalt were interpreted in terms of Density Functional Theory calculations in order to explain photolysis behavior. The photolysis of each compound depends selectively on the irradiation wavelength. Irradiation with 340-460 nm light and with the 488 nm laser line generates photolysis only in silver and thallium hyponitrite salts, while 253.7 nm light photolyzed all the studied compounds. Infrared spectroscopy was used to follow the photolysis process and to identify the generated products. Remarkably, gaseous N 2 O was detected after photolysis in the infrared spectra of sodium, silver, and thallium hyponitrite KBr pellets. The spectra for [Co(NH 3) 5-N(O)-NO-Co(NH 3) 5 ] 4+ suggest that one cobalt ion remains bonded to N 2 O from which the generation of a [(NH 3) 5 CoNNO] +3 complex is inferred. Density Functional Theory (DFT) based calculations confirm the stability of this last complex and provide the theoretical data which are used in the interpretation of the electronic spectra of the hyponitrite ion and the cobalt binuclear complex and thus in the elucidation of their photolysis behavior. Carbonate ion is also detected after photolysis in all studied compounds, presumably due to the reaction of atmospheric CO 2 with the microcrystal surface reaction products. Kinetic measurements for the photolysis of the binuclear complex suggest a first order law for the intensity decay of the hyponitrite IR bands and for the intensity increase in the N 2 O generation. Predicted and experimental data are in very good agreement.
Acta Crystallographica Section A Foundations of Crystallography, 2009
Page s 250 transition metal elements TM = E8-E10. In the system Ba-Ni-Ge, two homogeneity ranges ... more Page s 250 transition metal elements TM = E8-E10. In the system Ba-Ni-Ge, two homogeneity ranges with different Ni content are structurally characterized, which are both related to the clathrate-I structure. Compounds with low Ni content, Ba 8 Ni x Ge 42±1 (0 < x ≤ 0.6), can be considered as solution of Ni in the binary Ba 8 Ge 43 3 (space group Ia-3d, a = 21.307(2) Å). The subcell with space group Pm-3n is observed for the compositions Ba 8 Ni x Ge 42±1 (0.6 < x ≤ 4.2). The change in Ni content is associated with the respective change in lattice parameters (a = 10.657(1)-10.681(1) Å), but also confirmed by microprobe analyses.
Vibrational Spectroscopy, 2000
Ž w Ž. x. Interferometric infrared and Raman spectra of thallium nitroprusside Tl Fe CN NO , with... more Ž w Ž. x. Interferometric infrared and Raman spectra of thallium nitroprusside Tl Fe CN NO , with normal isotopic composi-2 5 13 Ž. y1 Ž. tion or substituted with C 98.5% , were obtained from 4000 to 50 cm at room and low temperature boiling liquid air. Infrared microscopy used with selected monocrystals allowed the detection of very weak overtone and combination bands. Comparisons are made with other nitroprusside salts, anhydrous and hydrated, and especially with sodium nitroprusside dihydrate.
Vibrational Spectroscopy, 1997
... [8]. ME Chacón Villalba. In: (72nd ed.),Doctoral Thesis, Facultad de Ciencias Exactas, Univer... more ... [8]. ME Chacón Villalba. In: (72nd ed.),Doctoral Thesis, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, R. Argentina (1995). [9]. ME Chacón Villalba, EL Varetti, PJ Aymonino, Part II, submitted for publication. [10]. R. Marqués. In: (72nd ed.),Rep. No. ...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2001
Infrared spectra of the metastable state I (MSI) of normal and 15NO, N18O and 54Fe isotopically s... more Infrared spectra of the metastable state I (MSI) of normal and 15NO, N18O and 54Fe isotopically substituted sodium nitroprusside dihydrate (Na2[Fe(CN)5NO].2H2O) have been obtained at 77 K. A comparison of the isotopic shifts measured for the vibrational modes of the FeXY (XY = NO or ON) moiety with those calculated by means of quantum chemistry (DFT) procedures supports the linear Fe-O = N arrangement for the MSI state.
Polyhedron, 2002
The crystal structure of nitropentaamminecobalt(III) nitroprusside sesquihydrate, [Co(NH 3) 5 NO ... more The crystal structure of nitropentaamminecobalt(III) nitroprusside sesquihydrate, [Co(NH 3) 5 NO 2 ][Fe(CN) 5 NO] ×/1.5H 2 O has been determined by Patterson and Fourier methods employing 3881 independent X-ray reflections with I /2s (I) and refined by full-matrix least-squares to R 1 0/0.032. The substance crystallizes in the monoclinic C 2/c (C 2h 6) space group No. 15, with a 0/ 28.408(3), b 0/6.422(1), c 0/22.401(3) Å , b 0/123.55(1)8 and Z0/8. The metastable state I (MSI) of the nitroprusside anion and the photochemical isomerization reaction of the nitropentaamminecobalt(III) cation to the nitrito isomer were produced by irradiation with Ar ' laser light of 488 nm wavelength at 77 K. TGA and DTA of the non-excited substance were performed under nitrogen atmosphere.
Journal of Raman Spectroscopy, 1991
Journal of Molecular Structure, 2011
4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) was purified and characterized. A new copper(II) comp... more 4-Chloro-2-nitrobenzenesulfonamide (ClNbsa) was purified and characterized. A new copper(II) complex, [Cu(ClNbsa) 2 (NH 3) 2 ], has been prepared using the sulfonamide as ligand. The thermal behavior of both, the ligand and the Cu(II) complex, was investigated by thermogravimetric analyses (TG) and differential thermal analysis (DT), and the electronic characteristics analyzed by UV-VIS, FTIR, Raman and 1 H NMR spectroscopies. The experimental IR, Raman and UV-VIS spectra have been assigned on the basis of DFT calculations at the B3LYP level of theory using the standard (6-31 + G ⁄⁄) basis set. The geometries have been fully optimized in vacuum and in modeled dimethylsulfoxide (DMSO) solvent, using for the latter a continuum solvation model that reproduced the experimental conditions of the UV-VIS spectroscopy. The theoretical results converged to stable conformations for the free sulfonamide and for the complex, suggesting for the latter a distorted square planar geometry in both environments.
Journal of Molecular Structure, 2012
Two ligands for coordination compounds incorporating benzimidazole moieties, namely 1,1′-butane-1... more Two ligands for coordination compounds incorporating benzimidazole moieties, namely 1,1′-butane-1,4diylbis(5,6-dimethyl-1H-benzimidazole) and 1,1′-butane-1,4-diylbis(1H-benzimidazole), are synthesized and then characterized both experimentally and theoretically. Their structures are studied by single crystal X-ray diffraction, UV-Vis spectroscopy, and FT-IR spectroscopy. The optimized geometries, vibrational frequencies, vertical excitation energies of the two ligands are calculated using the (TD)DFT/B3LYP/TZVP method. The calculated results reproduce the experimental data. Additional bonding information about the coordinated N atoms in the two ligands is obtained by FMO and NBO analysis to investigate the substitutegroup effect on the coordination ability. The results confirm that the ligand with electron-donating methyl groups on the benzimidazole moieties has a stronger coordination ability.
Journal of Chemical Crystallography - J CHEM CRYSTALLOGRAPHY, 2001
The crystal structure of tetrabutylammonium nitroprusside dihydrate (TBANPDH, [(C4H9)4N]2[Fe(CN)5... more The crystal structure of tetrabutylammonium nitroprusside dihydrate (TBANPDH, [(C4H9)4N]2[Fe(CN)5NO]·2H2O) was determined by single crystal X-ray diffraction (XRD) and the compound was also studied, as well as the anhydrous salt (TBANP), by room and low temperature Fourier Transform Infra-Red (FTIR) and room temperature Fourier Transform Near Infra-Red Raman (FTNIRR) spectroscopies. In addition to the ground states (GS), the metastable excited states (MSI and MSII) generated by laser excitation (488 nm) at low temperature were IR studied, both of the dihydrate and the anhydrate. TBANPDH crystallizes in the trigonal space group P3221, D63, with a = b = 13.777(2), c = 22.039(2) Å, and Z = 3. The structure was solved employing 1273 independent XR reflections, with I > 2s(I), by Patterson and Fourier methods and refined by full-matrix least-squares to R1 = 0.054.
Journal of Chemical Crystallography, 2007
... ME Chacón Villalba 4 EL Varetti (&) 4 PJ Aymonino Departamento de Quımica, Facultad d... more ... ME Chacón Villalba 4 EL Varetti (&) 4 PJ Aymonino Departamento de Quımica, Facultad de Ciencias Exactas, Centro de Quımica Inorgánica ... T, Al-Laham MA, Peng CY, Nanayakkara A, Gonzalez C, Challacombe M, Gill PMW, Johnson B, Chen W, Wong MW, Andres JL, Gonz ...
Inorganica Chimica Acta, 2006
The [(NH 3) 5 CoN(O)NOCo(NH 3) 5 ]Br 2 (NO 3) 2 AE 2.5H 2 O salt was studied by X-ray diffraction... more The [(NH 3) 5 CoN(O)NOCo(NH 3) 5 ]Br 2 (NO 3) 2 AE 2.5H 2 O salt was studied by X-ray diffraction methods. Such structural study confirmed the already reported binuclear, bridged structure of the complex cation and allowed a description of the main features of the lattice structure. An infrared and Raman study of that compound was also performed in order to revise the assignments of the vibrational features. Such spectroscopic study, aided by 14/15 N replacement and quantum chemistry calculations, permitted a reassignment of the spectral bands originated in the hyponitrite bridge.
Inorganic Chemistry, 2009
Lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphtoquinone) (HLap, C(15)H(14)O(3)) reacts with ... more Lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphtoquinone) (HLap, C(15)H(14)O(3)) reacts with Mn(2+) producing a novel polymeric complex with formula: [Mn(Lap)(2)](n). Two ligands chelate the metal through their ortho oxygen (O1, O2) moiety while two para oxygens, from other Lap ligands, complete the octahedral coordination sphere. Thus far, all reported Lap metal complexes are mononuclear, lack the metal-trans-quinonic (para) oxygen binding and have Lap as a bidentate ligand. Synthesis, X-ray diffraction, IR, and UV-visible spectroscopic properties, thermogravimetric analysis, and differential thermal analysis of this complex are reported along with a density functional theory study describing electron transfer from the Mn to the Lap ligand at low temperature. X-ray structure determinations at 125, 197, and 300 K describe the progressive trend of a Mn contribution to the Mn-O1 bond length as a function of T. The Mn-O1 bond distance increases with temperature and may be therefore associated with a semiquinonate action at low T by the carbonyl O1 donor (and corresponding to Mn(III)). It transforms to a more classical coordinative bond at room T and stabilizes a Mn(II) species; this is a reversible phenomenon involving Mn(II)-Mn(III) oxidation states.