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Oscar E. Piro

Bio: Oscar E. Piro is an academic researcher from National University of La Plata. The author has contributed to research in topics: Crystal structure & Monoclinic crystal system. The author has an hindex of 31, co-authored 276 publications receiving 3639 citations. Previous affiliations of Oscar E. Piro include National Scientific and Technical Research Council.


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TL;DR: Results showed that structural modifications on the semicarbazone moiety could have a significant effect on the anti-tumor activity of the vanadium complexes, and no apparent correlation could be demonstrated between reduction potentials of the complexes and their anti-Tumor activities.

113 citations

Journal ArticleDOI
TL;DR: The interaction of lower rim calix(4)arene derivatives containing ester (1) and ketone (2) functional groups and bivalent (alkaline-earth, transition- and heavy-metal) cations has been investigated in various solvents and the selective behavior of 1 and 2 for bivalent cations is demonstrated for the first time.
Abstract: The interaction of lower rim calix(4)arene derivatives containing ester (1) and ketone (2) functional groups and bivalent (alkaline-earth, transition- and heavy-metal) cations has been investigated in various solvents (methanol, N,N-dimethylformamide, acetonitrile, and benzonitrile). Thus, 1 H NMR studies in CD 3 -OD, C 3 D 7 NO, and CD 3 CN show that the interaction of these ligands with bivalent cations (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Hg 2+ , Pb 2+ , Cd 2+ ) is only observed in CD 3 CN. These findings are corroborated by conductance measurements in these solvents including benzonitrile, where changes upon the addition of the appropriate ligand (1 or 2) to the metal-ion salt only occur in acetonitrile. Thus, in this solvent, plots of molar conductance against the ligand/metal cation ratio reveal the formation of 1:1 complexes between these ligands and bivalent cations. Four metal-ion complex salts resulting from the interaction of 1 and 2 with cadmium and lead, respectively, were isolated and characterized by X-ray crystallography. All four structures show an acetonitrile molecule sitting in the hydrophobic cavity of the ligand. The mode of interaction of the neutral guest in the cadmium(II) complexes differs from each other and from that found in the lead(II) complexes and provides evidence of the versatile behavior of acetonitrile in binding processes involving calix(4)arene derivatives. The thermodynamics of complexation of these ligands and bivalent cations in acetonitrile is reported. Thus, the selective behavior of 1 and 2 for bivalent cations is for the first time demonstrated. The role of acetonitrile in the complexation process in solution is discussed on the basis of 1 H NMR and X-ray crystallographic studies. It is suggested that the complexation of 1 and 2 with bivalent cations is likely to involve the ligand-solvent adducts rather than the free ligand. Plots of complexation Gibbs energies against the corresponding data for cation hydration show a selectivity peak which is explained in terms of the predominant role played by cation desolvation and ligand binding energy in complex formation involving metal cations and macrocycles in solution. A similar peak is found in terms of enthalpy suggesting that for most cations (except Mg 2+ ) the selectivity is enthalpically controlled. The ligand effect on the complexation process is quantitatively assessed. Final conclusions are given highlighting the role of the solvent in complexation processes involving calix(4)arene derivatives and metal cations.

86 citations

Journal ArticleDOI
TL;DR: The ground and excited state properties of the newly prepared complexes Re(CO)3(2,2'biquinoline)LS+, LS = pyrazine or 4,4'bipyridine, and Re( CO)3 (2, 2 'bipy)(2-pyrazinecarboxylate) were investigated by steady state and time-resolved spectroscopy as mentioned in this paper.

83 citations

Journal ArticleDOI
TL;DR: In this article, the new dioxo(semicarbazone)vanadium(V) complexes cis-VO2L have been synthesized, characterized by 1H and 13C NMR and FTIR spectroscopy and tested for bioactivity as potential insulin mimetic agents.
Abstract: The new dioxo(semicarbazone)vanadium(V) complexes cis-VO2L, where L = salicylaldehyde semicarbazone (L1), salicylaldehyde 4-n-butylsemicarbazone (L2), or salicylaldehyde 4-(2-naphthyl)semicarbazone (L3), have been synthesized, characterized by 1H and 13C NMR and FTIR spectroscopy and tested for bioactivity as potential insulin-mimetic agents. All dioxovanadium(V) complexes exhibited essentially no in vitro insulin-mimetic activity, but the VO2L2 complex developed activity in the presence of ascorbic acid, similar to that of vanadyl sulfate. The molecular structure of the novel complex VO2L1 has been solved by X-ray diffraction methods. It crystallizes in the tetragonal space group P42/n with a = 12.7674(7), c = 11.5308(5) A, and Z = 8. The vanadium atom is in a distorted square-pyramidal coordination, with L1 acting as a tridentate ligand through its azomethyne nitrogen atom, carbonyl oxygen atom and deprotonated phenol oxygen atom. The coordination sphere is completed by two oxo ligands at cis positions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

71 citations

Journal ArticleDOI
TL;DR: In this article, the synthesis and characterization of a series of new Ru(II) complexes with different antitrypanosomal active compounds is presented, where ruthenium clotrimazole complexes are more active against Trypanosoma cruzi, causative agent of Chagas' disease, than the corresponding free ligand.

52 citations


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TL;DR: This volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of the instrument and its ancillary tools are simply and well presented.
Abstract: I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

3,197 citations

01 Jan 2016
TL;DR: The principles of fluorescence spectroscopy is universally compatible with any devices to read and is available in the digital library an online access to it is set as public so you can download it instantly.
Abstract: Thank you very much for downloading principles of fluorescence spectroscopy. As you may know, people have look hundreds times for their favorite novels like this principles of fluorescence spectroscopy, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some harmful bugs inside their desktop computer. principles of fluorescence spectroscopy is available in our digital library an online access to it is set as public so you can download it instantly. Our digital library spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the principles of fluorescence spectroscopy is universally compatible with any devices to read.

2,960 citations

01 Feb 1995
TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.
Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

1,652 citations