Daniel Vega

Comisión Nacional de Energía Atómica, Buenos Aires, Buenos Aires F.D., Argentina

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Publications (48)63.35 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: This manuscript presents a structural, thermal and spectroscopic characterization of two different solid state forms of drospirenone (C24 H30 O3), a crystalline phase and an amorphous one. The molecule contains three fused six-membered rings and two five-membered rings; none of them is planar in character.An intra-molecular hydrogen bond was observed in the crystalline phase. Although the melting point is 202(1) °C, only very weak interactions could be considered responsible for the packing in the crystal.The amorphous phase was obtained from molten material and was found five times more soluble than the crystalline one.Infrared and Raman spectra for both phases were recorded and the vibrational properties were calculated using the GAUSSIAN 03 software package; overall agreement between calculations and experiment was obtained.
    Journal of Molecular Structure 05/2013; 1040:83–89. · 1.40 Impact Factor
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    ABSTRACT: The synthesis, X-ray structure and magnetic properties of two new zoledronato complexes are presented: Mn(II)(H3Zol)2(H2O)2, (I) and Fe(III)15(HZol)10(H2Zol)2 (H2O)24 (2/3Cl:1/3H2O)6·7Cl·65(H2O) (II), where H4Zol = zoledronic acid = C5H10N2O7P2. Complex (I) is a dimer, built up around an inversion centre where the cation is located, surrounded by two chelating zoledronate anions and two water molecules. The structure is isomorphous to the Co, Ni and Zn isologues. A quite different structure is the Fe(III) complex which consists of a centrosymmetric cluster with 15 Fe(III) cations (one of them at the inversion centre), 12 zoledronate anions, in different protonation states and 26 coordinated water molecules, 24 of which show full occupancy and the remaining 2 share 6 coordination sites with 4 chlorine anions. There are in addition 7 chlorine counterions and a not well determined number of hydration water molecules, their number being adjusted as to match the chemical and TGA analysis. The general shape of the molecule is that of a 6 arm propeller with a Fe(III) cation at its center and two FeO6 coordination polyhedra sitting above and below, defining some sort of “paddle wheel axis”, perpendicular to the wheel plane. Around this axis there is an almost perfect circular structure formed by other six FeO6 octahedra, to which the “paddles”, defined by the remaining six FeO6 groups attach. The ensemble presents some unusual (Fe···OPO)n loops (n = 2,3,4), some of them unreported, and displays a striking non-crystallographic −3 symmetry. The protonation state of the zoledronato ligands were inferred from the counterions effectively found and charge balance considerations. Both compounds present a paramagnetic behaviour at R.T, and obey a Curie Weiss law down to rather low temperatures (15 K for (I), 100(K) for (II)) with a tendency to different types of interactions viz., ferromagnetic for (I) and antiferromagnetic for (II). The geometry of the F15 cluster is analyzed.
    Inorganica Chimica Acta 01/2013; 394:229–236. · 1.69 Impact Factor
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    ABSTRACT: Crystal structures of polymorphs α and β of imatinib mesylate were obtained. Thermal behavior and grinding effects were studied by X-ray powder diffraction and differential scanning calorimetry techniques. Molecules in forms α and β exhibit significant conformational differences due to dissimilar intramolecular interactions, which stabilize their molecular conformations. In spite of that, both crystal structures present a dimer-chain arrangement. Dimers are mainly determined by hydrogen bonding interactions and some weak π-π interactions. Connections between dimers are provided by mesylate ions to determine chains of dimers. Neighboring chains are linked by very weak interactions: C-H···π interactions in form α and π-π interactions in form β. At room temperature, thermal disorder was observed in the mesylate ion in form α, which could be removed at low temperatures (-123°C). Form β was found to be the more stable form at room temperature. Both polymorphs exhibit a tendency to generate amorphous material by grinding, which can be converted to a crystalline phase by either temperature or aging. When amorphous crystallization is kinetically studied at room temperature, form β is obtained after a week. Conversely, when the crystallization is activated by temperature, the final obtained crystal form depends on the starting material, proving the importance of seeding.
    Journal of Pharmaceutical Sciences 02/2012; 101(2):541-51. · 3.13 Impact Factor
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    ABSTRACT: In this work only one diastereomer of benzamarone (1,2,3,4,5-pentaphenylpentan-1,5-dione) 1 was isolated from tandem condensation/addition reaction between deoxybenzoin and benzaldehyde in alkaline medium and by Michael addition of deoxybenzoin to (E)-2-phenylchalcone. Compound 1 was investigated by single crystal X-ray diffraction: C35H28O2, Mr = 480.57, triclinic system, space group P1 with unit cell parameters a = 11.489(2), b = 11.669(2), c = 11.855(2) Å, α = 104.31(4), β = 116.91(3), γ = 98.96(3)°, V = 1305.6(4) Å3, Z = 2, T = 25(2) °C, ρcalc = 1.222 gr/cm3, μ = 0.074 mm−1. This study allowed us to assign the configuration 2R,4R/2S,4S corresponding to the diastereomer racemate C (Fig. 1) due to the fact that the crystal structure exhibits two independent molecules in the unit cell. Data obtained using NMR spectroscopy [1D and 2D NMR] are agreement with those obtained by X-ray diffraction. By comparison of NMR data, the configuration corresponding to the diastereomer racemate C was assigned to other substituted benzamarones synthesized by us, which present two and three stereocenters in their structure.
    Journal of Molecular Structure 02/2011; 987(s 1–3):119–125. · 1.40 Impact Factor
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    ABSTRACT: Abstract Two crystal structures of sulfonamide salts were studied by X-Ray diffraction. The compound C2H5N4O2S2 +·H2O·Cl− (I), (Hats·H2O·Cl, Hats = protonated 5-amino-2-sulfonamide-1,3,4-thiadiazole) crystallizes in orthorhombic space group, P212121, with unit cell parameters a = 10.047(4), b = 5.186(2), c = 16.766(6) Å and the compound C2H5N4O2S2 +·CH3O3S− (II), crystallizes in monoclinic space group, Cc, with unit cell parameters a = 5.378(3), b = 19.707(6), c = 10.014(5) Å, beta = 99.97(1)°. The molecules in compound I are arranged in a helix of alternating water and Hats molecules. Helixes are interconnected by hydrogen bonds provided by Cl− ions and one ring with a graph set R64 (12) is determined. The crystal structure of compound II presents mesylate and Hats molecules bonded by two hydrogen bond determining a ring with a graph set R22(8). Index abstract Two substituted sulfonamide salts were obtained, the hydrochloride is monohydrate and develops a helix arrangement of alternating water/sulfonamide molecules, meanwhile the mesylate is bonded to sulfonamide molecule determining a ring, with a graph set R22(8).
    Journal of Chemical Crystallography 01/2011; 41(8):1114-1119. · 0.51 Impact Factor
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    ABSTRACT: The reaction of copper acetate with 3,4,5-tri(ethoxy)benzoic acid leads to the formation of dodecakis((μ-(3,4,5-tri(ethoxy))benzoato-κ2O:O′)-hexa(copper(II)), [Cu6(O2CC6H2(OCH2CH3)3)12]. The new compound crystallizes in the triclinic system, space group P1¯ with Z=2, solvated by disordered cyclohexane molecules. The Cu(II) ions are placed in O5 pentacoordinated environments provided by four carboxylate oxygen atoms in a pseudo square planar arrangement and a fifth oxygen atom that belongs to a more distant carboxylate group in the axial position. The Cu(II) centers occupy the corners of a trigonal antiprism. A carboxylato network links each copper center with other four, providing potential paths for exchange coupling between the Cu(II) centers. Variable temperature magnetic susceptibility measurements show a maximum at 8K. An analysis based on the spin-Hamiltonian formalism and DFT-based broken symmetry computations provides insight into the magnetic exchange interactions between the metal centers.
    Inorganica Chimica Acta - INORG CHIM ACTA. 01/2011; 374(1):499-505.
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    ABSTRACT: Solid-state forms of zoledronic acid, a nitrogen-containing bisphosphonate used for treatment of bone diseases are studied using different experimental techniques (DSC, TG, and XRD). Two degrees of hydration have been obtained, containing one and three water molecules per zoledronic acid molecule. The crystal structure of the trihydrated form is reported. Two different anhydrated forms have been obtained when the hydrated ones were heated. Besides, during the dehydration process, an amount of metastable amorphous phase appears, as a function of the dehydration rate. The stability of the obtained crystalline forms is examined under high humidity and a different trihydrated form was obtained, setting clear that the same degree of hydration (trihydrated) can be obtained in two different crystalline forms, and then very different thermal behaviors have been observed.
    Journal of Pharmaceutical Sciences 12/2010; 99(12):4962-72. · 3.13 Impact Factor
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    ABSTRACT: The "aging-driven" decomposition of zolpidem hemitartrate hemihydrate (form A) has been followed by X-ray powder diffraction (XRPD), and the crystal and molecular structures of the decomposition products studied by single-crystal methods. The process is very similar to the "thermally driven" one, recently described in the literature for form E (Halasz and Dinnebier. 2010. J Pharm Sci 99(2): 871-874), resulting in a two-phase system: the neutral free base (common to both decomposition processes) and, in the present case, a novel zolpidem tartrate monohydrate, unique to the "aging-driven" decomposition. Our room-temperature single-crystal analysis gives for the free base comparable results as the high-temperature XRPD ones already reported by Halasz and Dinnebier: orthorhombic, Pcba, a = 9.6360(10) Å, b = 18.2690(5) Å, c = 18.4980(11) Å, and V = 3256.4(4) Å(3). The unreported zolpidem tartrate monohydrate instead crystallizes in monoclinic P2(1), which, for comparison purposes, we treated in the nonstandard setting P112(1) with a = 20.7582(9) Å, b = 15.2331(5) Å, c = 7.2420(2) Å, γ = 90.826(2)°, and V = 2289.73(14) Å(3). The structure presents two complete moieties in the asymmetric unit (z = 4, z' = 2). The different phases obtained in both decompositions are readily explained, considering the diverse genesis of both processes. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci.
    Journal of Pharmaceutical Sciences 10/2010; · 3.13 Impact Factor
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    ABSTRACT: Diaquabis[dihydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonato-kappa(2)O,O']magnesium(II), [Mg(C(5)H(9)N(2)O(7)P(2))(2)(H(2)O)(2)], consists of isolated dimeric units built up around an inversion centre and tightly interconnected by hydrogen bonding. The Mg(II) cation resides at the symmetry centre, surrounded in a rather regular octahedral geometry by two chelating zwitterionic zoledronate(1-) [or dihydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonate] anions and two water molecules, in a pattern already found in a few reported isologues where the anion is bound to transition metals (Co, Zn and Ni). catena-Poly[[aquacalcium(II)]-mu(3)-[hydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonato]-kappa(5)O:O,O':O',O''], [Ca(C(5)H(8)N(2)O(7)P(2))(H(2)O)](n), consists instead of a Ca(II) cation in a general position, a zwitterionic zoledronate(2-) anion and a coordinated water molecule. The geometry around the Ca(II) atom, provided by six bisphosphonate O atoms and one water ligand, is that of a pentagonal bipyramid with the Ca(II) atom displaced by 0.19 A out of the equatorial plane. These Ca(II) coordination polyhedra are ;threaded' by the 2(1) axis so that successive polyhedra share edges of their pentagonal basal planes. This results in a strongly coupled rhomboidal Ca(2)-O(2) chain which runs along [010]. These chains are in turn linked by an apical O atom from a -PO(3) group in a neighbouring chain. This O-atom, shared between chains, generates strong covalently bonded planar arrays parallel to (100). Finally, these sheets are linked by hydrogen bonds into a three-dimensional structure. Owing to the extreme affinity of zoledronic acid for bone tissue, in general, and with calcium as one of the major constituents of bone, it is expected that this structure will be useful in modelling some of the biologically interesting processes in which the drug takes part.
    Acta Crystallographica Section C Crystal Structure Communications 06/2010; 66(Pt 6):m166-70. · 0.78 Impact Factor
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    ABSTRACT: The title compound, {[Na(3)(C(5)H(9)N(2)O(7)P(2))(2)(C(5)H(9.5)N(2)O(7)P(2))(2)(H(2)O)(4)].2H(2)O}(n), (II), is polymeric and consists of undulating chains parallel to [011] interconnected by hydrogen-bonding and pi-pi interactions. There are two independent Na(+) cations in the asymmetric unit (one lying on an inversion centre), two zoledronate anions and three water molecules, two of which are coordinated and one of which is a free solvate. Each cation is surrounded in an octahedral fashion by O atoms from four different zoledronate units and two/one coordinated water molecules. The zoledronate groups present their usual zwitterionic character, with negative charges in the protonated phosphonates and a positive charge at the protonated imidazole N atom. Two symmetry-related phosphonate groups share (in the form of a very strong linear hydrogen bond) an H atom lying on a symmetry centre, midway between the O atoms involved. The zoledronate binding modes present in (II) are both unreported for bisphosphonate anions. Intra- and inter-chain interactions are enhanced by a variety of hydrogen bonds where all the available O-H and N-H donors are involved, in addition to a strong imidazole-phosphonate C-H...O interaction, typical in these kinds of structures.
    Acta Crystallographica Section C Crystal Structure Communications 04/2010; 66(Pt 4):m122-6. · 0.78 Impact Factor
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    ABSTRACT: The title compound, {[K(C(5)H(9)N(2)O(7)P(2))(H(2)O)].H(2)O}(n), is polymeric and consists of layers parallel to (001) interconnected by hydrogen-bonding and pi-pi interactions. The K(+) cation is eightfold coordinated in a KO(8) environment by O atoms from three different chelating zoledronate units and two coordinated water molecules. The zoledronate group presents its usual zwitterionic character, with negative charges in the singly protonated phosphonate groups and a positive charge at the protonated imidazole N atom. The anion binds to three different K(+) cations in a (so far unreported) triply chelating manner. Intra- and interplanar interactions are enhanced by a variety of hydrogen bonds involving all available O-H and N-H donors. A strong imidazole-phosphonate C-H...O interaction is present in the structure.
    Acta Crystallographica Section C Crystal Structure Communications 01/2010; 66(Pt 1):m13-6. · 0.78 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 26(30).
  • Eleonora Freire, Daniel R. Vega, Ricardo Baggio
    Acta Crystallographica Section C-crystal Structure Communications - ACTA CRYSTALLOGR C-CRYST STR. 01/2010; 66(1).
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    ABSTRACT: The compound 1,c-3-diphenyltetran-r-1-ol (systematic name: 1,c-3-diphenyl-1,2,3,4-tetrahydro-r-1-naphthol), C(22)H(20)O, which possesses the tetrahydronaphthalene core that is found in a large number of natural products, crystallizes with Z' = 4 and with the four molecules forming a hydrogen-bonded cyclic aggregate. The aliphatic six-membered rings are present with two different conformations in the molecules of the asymmetric unit. A comparison with similar fragments reveals their conformational flexibility. In addition, the structure demonstrates the relative stereochemistries of the chiral centers, which are important since the title compound is used in the stereoselective synthesis of compounds with therapeutic activity.
    Acta Crystallographica Section C Crystal Structure Communications 03/2009; 65(Pt 2):o35-8. · 0.78 Impact Factor
  • Acta Crystallographica Section C-crystal Structure Communications - ACTA CRYSTALLOGR C-CRYST STR. 01/2009; 65(2).
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    Eleonora Freire, Daniel R Vega
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    ABSTRACT: In the title complex, [Zn(C(5)H(9)NO(7)P(2))(2)(H(2)O)]·2H(2)O, the zinc atom is coordinated by two zoledronate anions [zoledronate = (2-(1-imidazole)-1-hydr-oxy-1,1'-ethyl-idenediphophonate)] and one water mol-ecule. The coordination number is 5. There is one half-mol-ecule in the asymmetric unit, the zinc atom being located on a twofold rotation axis passing through the metal centre and the coordinating water O atom. The anion exists as a zwitterion with an overall charge of -1; the protonated nitro-gen in the ring has a positive charge and the two phospho-nates groups each have a single negative charge. Inter-molecular O-H⋯O hydrogen bonds link the mol-ecules. An N-H⋯O inter-action is also present.
    Acta Crystallographica Section E Structure Reports Online 01/2009; 65(Pt 11):m1430-1. · 0.35 Impact Factor
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    ABSTRACT: In this work we investigate the room-temperature Raman spectra of several rare-earth [RE(HCOO)(3); RE = La, Pr, Nd, Gd, Tb and Y] formates. Polarized measurements were carried out for La(HCOO)(3) yielding the observation of most of the Raman-active phonons predicted by group theory analysis. The respective assignment is given based on the formate vibrations and correlations with previous results in other RE(HCOO)(3) systems. The wavenumber 'softening' observed when RE goes from Y to La is accounted for the lattice expansion. Copyright (C) 2009 John Wiley & Sons, Ltd.
    Journal of Raman Spectroscopy 01/2009; 40:954-957. · 2.68 Impact Factor
  • Eleonora Freire, Daniel R. Vega
    Acta Crystallographica Section E-structure Reports Online - ACTA CRYSTALLOGR E-STRUCT REP. 01/2009; 65(11).
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    Eleonora Freire, Daniel R Vega
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    ABSTRACT: In the title complex, [Zn(C(5)H(9)NO(7)P(2))(2)(H(2)O)(2)], the zinc atom is coordinated by two bidentate zoledronate [zoledronate = (2-(1-imidazole)-1-hydr-oxy-1,1'-ethyl-idenediphophonate)] ligands and two water mol-ecules. The coordination number is 6. There is one half-mol-ecule in the asymmetric unit with the zinc atom located on a crystallographic inversion centre. The anion exists as a zwitterion with an overall charge of -1; the protonated nitro-gen in the ring has a positive charge and the two phospho-nates groups each have a single negative charge. There are two intra-molecular O-H⋯O hydrogen bonds. The mol-ecules are linked into a chain by inter-molecular O-H⋯O hydrogen bonds. Adjacent chains are further linked by O-H⋯O hydrogen bonds involving the aqua ligands. An N-H⋯O inter-action is also observed.
    Acta Crystallographica Section E Structure Reports Online 01/2009; 65(Pt 11):m1428-9. · 0.35 Impact Factor
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    ABSTRACT: Two crystalline forms (forms I and II) and an amorphous phase of bicalutamide were fully characterized through combined results of differential scanning calorimetry, X-ray powder and single crystal diffraction and Raman spectroscopy. Each polymorph crystallizes with one molecule in the asymmetric unit and the molecular conformations are quite different between them. The main difference is provided by C12-C11-S8-C5 torsion angle, which assumes a value of -88.3(4) degrees (-Syn-Clinal) and 72.5(4) degrees (+Syn-Clinal) in forms I and II, respectively. Consequently, molecules in form I show an open folding and molecules in form II a closed one. The relative stability between forms I and II is presented in an energy versus temperature diagram, where forms I and II are considered as a monotropic system, being form I the more stable one. The amorphous phase was observed very metastable and it converts to form II spontaneously at RT in around a week.
    International Journal of Pharmaceutics 02/2007; 328(2):112-8. · 3.99 Impact Factor

Publication Stats

132 Citations
63.35 Total Impact Points

Institutions

  • 1995–2013
    • Comisión Nacional de Energía Atómica
      • Departamento de Física
      Buenos Aires, Buenos Aires F.D., Argentina
  • 2010
    • University of Buenos Aires
      Buenos Aires, Buenos Aires F.D., Argentina
  • 2003–2009
    • National University of General San Martín
      • Escuela de Ciencia y Tecnología
      San Martín, Provincia de San Juan, Argentina
  • 2007
    • University of Duisburg-Essen
      • Physikalische Chemie Arbeitsgruppe
      Duisburg, North Rhine-Westphalia, Germany