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Enrique J. Baran

Bio: Enrique J. Baran is an academic researcher from National University of La Plata. The author has contributed to research in topics: Infrared spectroscopy & Raman spectroscopy. The author has an hindex of 32, co-authored 589 publications receiving 6392 citations. Previous affiliations of Enrique J. Baran include Technical University of Dortmund & National Scientific and Technical Research Council.


Papers
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Journal ArticleDOI
TL;DR: In this article, a review of synthetic oxalato-complexes analogous to these natural species, including usual synthetic procedures and a thorough analysis of their crystallographic and structural peculiarities is presented.
Abstract: Four iron-containing natural oxalates, usually classified as organic minerals, are known (humboldtine, minguzzite, stepanovite and zhemchuzhnikovite). Their occurrences and general properties are presented and briefly discussed. The subsequent part of the review is devoted to the discussion of synthetic oxalato-complexes, analogous to these natural species, including usual synthetic procedures and a thorough analysis of their crystallographic and structural peculiarities. The thermal, spectroscopic and magnetic properties of these complexes are also analyzed in detail and comparisons with other closely related complexes are also included in the discussions.

12 citations

Journal ArticleDOI
TL;DR: In this paper, the assymetric stretching frequencies of barium manganates (V) (VI) and (VII), chromate (V), and ortho vanadate and other T d -transition barium oxometalates are correlated with the electronic structure of the complex anions.

12 citations

Journal Article
01 Jan 1999-Afinidad
TL;DR: The infrared spectra of the bis-chelated Cu(I1) complexes of the amino acids glycine, alanine, leucine, isoleuceine, valine and phenylalanine were recorded and analyzed in relation to its structural peculiarities as discussed by the authors.
Abstract: SUMMARY. The infrared spectra of the bis-chelated Cu(I1) complexes of the amino acids glycine, alanine, leucine, isoleuceine, valine and phenylalanine, which posses different kind of pharmacologic activity, were recorded and analyzed in relation to its structural peculiarities. Some comparisons between the recorded spectra are also presented and the characteristics of the carboxylate motions as well as those of the metal-to-ligand vibrations are discussed in detail. RESUMEN. "Espectros de Infrarrojo de los Complejos de Cobre(I1) de Aminoacidos con Residuos Hidrofobicos". Los espectros de infrarrojo de los complejos de Cu(II), bisquelados con los aminoacidos glicina, alanina, leucina, isoleucina, valina y fenilalanina, conocidos por presentar diferentes tipos de actividad farmacologica, fueron registrados y analizados en base a sus peculiaridades estructurales. Asimismo, se presentan algunas comparaciones entre los espectros obtenidos y las caracteristicas de las vibraciones asociadas a los grupos carboxilato y a las uniones metal-ligando se discuten en detalle.

12 citations

Journal ArticleDOI
TL;DR: In this article, the infrared and laser-Raman spectra of synthetic carnotite, K2[(UO2)2V2O8], are reported and discussed.
Abstract: The infrared and laser-Raman spectra of synthetic carnotite, K2[(UO2)2V2O8], are reported and discussed. Force constants for the terminal V-O bonds as well as for the UO22+ ions are evaluated. From the spectroscopic data, a U-O bond length of 1.81 A is estimated for the uranyl ion in this compound.

12 citations

01 Jan 2004
TL;DR: In this paper, a copper-II complex of the amino acid L-tryptophan, of stroichiometry Cu(Trp)2, was obtained from aqueous solution and its structural characteristics were deduced from the careful analysis of infrared, Raman and electronic absorption spectra, complemented with magnetic susceptibility measurements in the temperature range between 2 and 300 K.
Abstract: SUMMARY. A copper(II) complex of the amino acid L-tryptophan, of stroichiometry Cu(Trp)2, was obtained from aqueous solution. Its structural characteristics were deduced from the careful analysis of infrared, Raman and electronic absorption spectra, complemented with magnetic susceptibility measurements in the temperature range between 2 and 300 K. The metal center presents a distorted octahedral CuN2O4 environment with a trans arrangement of the amino acids in the equatorial plane, involving the terminal amino and carboxylate groups. The coordination sphere is complemented with two longer apical Cu-O bonds involving “free” O-carboxylato atoms of neighboring complex moieties. RESUMEN. “ Comportamiento Espectrosco pico y Magne tico del Complejo de Cobre (II) con L-Triptofano ” . Un complejo de cobre (II) con el amino acido L-triptofano, de estequiometr ia Cu(Trp)2, fue obtenido de solucio n acuosa. Sus caracteristicas estructurales fueron deducidas en base a un pormenorizado an alisis de sus espectros de infrarrojo, Raman y de absorcio n electro nica, complementado con medidas de susceptibilidad magne tica en el intervalo de temperaturas entre 2 y 300 K. El centro met alico presenta un entorno CuN2O4 octae drico distorsionado con una disposicio n trans de los amino acidos en el plano ecuatorial, involucrando los grupos amino y carboxilato terminales. La esfera de coordinaci o n se complementa con dos enlaces Cu-O axiales mas largos, involucrando atomos de oxigeno “ libres” de grupos carboxilato de unidades complejas vecinas.

12 citations


Cited by
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Journal ArticleDOI
TL;DR: Aqueous V(III) Chemistry 877 6.2.1.
Abstract: 6.1.2. Aqueous V(III) Chemistry 877 6.1.3. Oxidation State of Vanadium in Tunicates 878 6.1.4. Uptake of Vanadate into Tunicates 879 6.1.5. Vanadium Binding Proteins: Vanabins 879 6.1.6. Model Complexes and Their Chemistry 880 6.1.7. Catechol-Based Model Chemistry 880 6.1.8. Vanadium Sulfate Complexes 881 6.2. Fan Worm Pseudopotamilla occelata 883 7. Vanadium Nitrogenase 883 7.1. Nitrogenases 883 7.2. Biochemistry of Nitrogenase 884 7.3. Clusters in Nitrogenase and Model Systems: Structure and Reactivity 885

1,184 citations

Journal ArticleDOI
TL;DR: In this paper, the perovskite structure is used to illustrate the relationship of structure to composition, and the history of the fundamental science of structure-to-composition is described.
Abstract: Starting with the history of the fundamental science of the relation of structure to composition delineated completely by Goldschmidt, we use the perovskite structure to illustrate the enormous pow...

998 citations

Journal ArticleDOI
TL;DR: Using a variety of approaches, researchers have begun to unravel the exquisite control mechanisms exerted by cells specialized for CaOx formation that include the machinery for uptake and accumulation of Ca, oxalic acid biosynthetic pathways, and regulation of crystal growth.
Abstract: Calcium oxalate (CaOx) crystals are distributed among all taxonomic levels of photosynthetic organisms from small algae to angiosperms and giant gymnosperms. Accumulation of crystals by these organisms can be substantial. Major functions of CaOx crystal formation in plants include high-capacity calcium (Ca) regulation and protection against herbivory. Ultrastructural and developmental analyses have demonstrated that this biomineralization process is not a simple random physical-chemical precipitation of endogenously synthesized oxalic acid and environmentally derived Ca. Instead, crystals are formed in specific shapes and sizes. Genetic regulation of CaOx formation is indicated by constancy of crystal morphology within species, cell specialization, and the remarkable coordination of crystal growth and cell expansion. Using a variety of approaches, researchers have begun to unravel the exquisite control mechanisms exerted by cells specialized for CaOx formation that include the machinery for uptake and accumulation of Ca, oxalic acid biosynthetic pathways, and regulation of crystal growth.

993 citations

01 Jan 1993
TL;DR: This work states that for many years, bone was defined anatomically and examined largely in a descriptive manner by ultrastructural analysis and by biochemical and histochemical methods, but now, complemented by an increased knowledge of molecular mechanisms that are associated with and regulate expression of genes encoding phenotypic compone...
Abstract: I. Introduction A FUNCTIONAL relationship between cell growth and the initiation and progression of events associated with differentiation has been a fundamental question challenging developmental biologists for more than a century. In the case of bone, as observed with other cells and tissue, the relationship of growth and differentiation must be maintained and stringently regulated, both during development and throughout the life of the organism, to support tissue remodeling. For many years, bone was defined anatomically and examined largely in a descriptive manner by ultrastructural analysis and by biochemical and histochemical methods. These studies provided the basis for our understanding of bone tissue organization and orchestration of the progressive recruitment, proliferation, and differentiation of the various cellular components of bone tissue. Now, complemented by an increased knowledge of molecular mechanisms that are associated with and regulate expression of genes encoding phenotypic compone...

982 citations

Journal ArticleDOI
TL;DR: A complete chemical and physicochemical characterization of chitin, chitosan and their derivatives is not possible without using spectroscopic techniques, so this review focuses on the application of Spectroscopic methods for the structural analysis of these compounds.
Abstract: Chitin, the second most important natural polymer in the world, and its N-deacetylated derivative chitosan, have been identified as versatile biopolymers for a broad range of applications in medicine, agriculture and the food industry. Two of the main reasons for this are firstly the unique chemical, physicochemical and biological properties of chitin and chitosan, and secondly the unlimited supply of raw materials for their production. These polymers exhibit widely differing physicochemical properties depending on the chitin source and the conditions of chitosan production. The presence of reactive functional groups as well as the polysaccharide nature of these biopolymers enables them to undergo diverse chemical modifications. A complete chemical and physicochemical characterization of chitin, chitosan and their derivatives is not possible without using spectroscopic techniques. This review focuses on the application of spectroscopic methods for the structural analysis of these compounds.

848 citations