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Beltrán A, Gracia L, Andrés J. Density functional theory study of the brookite surfaces and phase transitions between natural titania polymorphs. J Phys Chem B 2007; 110:23417-23. [PMID: 17107193 DOI: 10.1021/jp0643000] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The present study is concerned with the structural and electronic properties of the low-index surfaces of the brookite form of titanium dioxide. A theoretical investigation is carried out using the density functional formalism under the nonlocal B3LYP approximation to calculate surface energies, band energy values, and to interpret the response to hydrostatic pressure of the bulk and surfaces of the brookite structure. In addition, phase transformations with pressure are predicted from the anatase and the rutile to the brookite polymorph at about 3.8 and 6.2 GPa, respectively. The orthorhombic structure and the fractional coordinates of brookite vary isotropically with the rise in pressure. The calculated band gap energy is 3.78 eV for the bulk brookite. The brookite surface stabilities follow the sequence (010) < (110) < (100), and the minimum gap energy value is found for the (110) surface.
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Martí S, Andrés J, Silla E, Moliner V, Tuñón I, Bertrán J. Computer-Aided Rational Design of Catalytic Antibodies: The 1F7 Case. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200603293] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Ramos D, Castillo R, Canle L. M, García M, Andrés J, Santaballa J. Density functional study of the Hoffmann elimination of (N-Cl),N-methylethanolamine in gas phase and in aqueous solution. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.08.055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Visart de Bocarmé T, Chau TD, Tielens F, Andrés J, Gaspard P, Wang RLC, Kreuzer HJ, Kruse N. Oxygen adsorption on gold nanofacets and model clusters. J Chem Phys 2006; 125:054703. [PMID: 16942237 DOI: 10.1063/1.2227396] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have studied oxygen interaction with Au crystals (field emitter tips) using time-resolved (atom-probe) field desorption mass spectrometry. The results demonstrate no adsorption to take place on clean Au facets under chosen conditions of pressures (p < 10(-4) m/bar) and temperatures (T = 300-350 K). Steady electric fields of 6 V/nm do not allow dissociating the oxygen molecule. The measured O2+ intensities rather reflect ionization of O2 molecules at critical distances above the Au tip surface. Certain amounts of Au-O2 complex ions can be found at the onset of Au field evaporation. Calculations by density functional theory (DFT) show weak oxygen end-on interaction with Au10 clusters (Delta E = 0.023 eV) and comparatively stronger interaction with Au1/Au(100) model surfaces (Delta E = 0.25 eV). No binding is found on {210} facets. Including (positive) electric fields in the DFT calculations leads to an increase of the activation energy for oxygen dissociation thus providing an explanation for the absence of atomic oxygen ions from the field desorption mass spectra.
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Guerra D, Castillo R, Andrés J, Fuentealba P, Aizman A, Contreras R. Homofugality: A new reactivity index describing the leaving group ability in homolytic substitution reactions. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.04.092] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Alves C, Carneiro A, Andrés J, Domingo L. A DFT study of the Diels–Alder reaction between methyl acrolein derivatives and cyclopentadiene. Understanding the effects of Lewis acids catalysts based on sulfur containing boron heterocycles. Tetrahedron 2006. [DOI: 10.1016/j.tet.2006.03.037] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Tielens F, Andrés J, Chau TD, de Bocarmé TV, Kruse N, Geerlings P. Molecular oxygen adsorption on electropositive nano gold tips. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.02.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Gracia L, Sambrano JR, Andrés J, Beltrán A. Mechanistic Insights into the Reaction between VO2+ and Propene Based on a DFT Study. Organometallics 2006. [DOI: 10.1021/om050971t] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Andrés J, Ferreri M. Chlamydia psittaci E LINFOMI DEGLI ANNESSI OCULARI: IMPLICAZIONI TERAPEUTICHE. MICROBIOLOGIA MEDICA 2005. [DOI: 10.4081/mm.2005.3423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Pérez P, Andrés J, Safont VS, Contreras R, Tapia O. Exploring Two-State Reactivity Pathways in the Cycloaddition Reactions of Triplet Methylene. J Phys Chem A 2005; 109:4178-84. [PMID: 16833743 DOI: 10.1021/jp044701k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Spin forbidden 1,2-cycloadditions of triplet methylene to alkenes have been theoretically studied as an example of the two-state reactivity paradigm in organic chemistry. The cycloadditions of triplet methylene to ethylene and the (E)- and (Z)-2-butene isomers show spin inversion after the transition state and therefore with no effect on the reaction rate. A local analysis shows that while triplet methylene addition to alkenes leading to the formation of a biradical intermediate is driven by spin polarization, the ring closure step to yield cyclopropane is a pericyclic process. We have found that at the regions in the potential energy surface where the spin crossover is likely to occur, the spin potential in the direction of increasing spin multiplicity, mu(+)(s), tends to equalize the one in the direction of decreasing spin multiplicity, mu(-)(s). This equalization facilitates the spin transfer process driven by changes in the spin density of the system.
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Tielens F, Andrés J, Van Brussel M, Buess-Hermann C, Geerlings P. DFT Study of Oxygen Adsorption on Modified Nanostructured Gold Pyramids. J Phys Chem B 2005; 109:7624-30. [PMID: 16851883 DOI: 10.1021/jp0501897] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Periodic DFT calculations are used to predict and investigate the adsorption behavior of molecular oxygen on Au, Au/Pt, and Pt surfaces. To obtain an array of pyramids containing surface atoms with the lowest possible coordination number, a nano-modified surface consisting of a symmetrically "modified" (100) surface was used. The effect of atom substitution (organized alloying) is investigated. The adsorption of molecular oxygen on a pure gold pyramid is exothermic by 0.77 eV for the end-on adsorption mode. In the case of a pure platinum pyramid, the end-on adsorption mode was found to dissociate; however, a side-on geometry was encountered with an energy of adsorption of 2.3 eV. This value is in line with the fact that the adsorption energy of small molecules does not vary much on Pt surfaces with different indices. Additionally, some geometrically related trends of the surface deformation in relation to its composition and after adsorption of molecular oxygen are highlighted.
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Sambrano JR, Gracia L, Andrés J, Berski S, Beltrán A. A Theoretical Study on the Gas Phase Reactions of the Anions NbO3-, NbO5-, and NbO2(OH)2- with H2O and O2. J Phys Chem A 2004. [DOI: 10.1021/jp047229b] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Gracia L, Andrés J, Safont VS, Beltrán A, Sambrano JR. DFT Study of the Reaction between VO2+ and C2H6. Organometallics 2004. [DOI: 10.1021/om0342098] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Gracia L, Sambrano JR, Safont VS, Calatayud M, Beltrán A, Andrés J. Theoretical Study on the Molecular Mechanism for the Reaction of VO2+ with C2H4. J Phys Chem A 2003. [DOI: 10.1021/jp0222696] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Calatayud M, Berski S, Beltran A, Andrés J. An atom-in-molecules and electron-localization-function study of the interaction between O 2 and V x O y + /V x O y ( x = 1, 2, y = 1-5) clusters. Theor Chem Acc 2002. [DOI: 10.1007/s00214-002-0350-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Alves C, da Silva A, Martı́ S, Moliner V, Oliva M, Andrés J, Domingo L. An AM1 theoretical study on the effect of Zn2+ Lewis acid catalysis on the mechanism of the cycloaddition between 3-phenyl-1-(2-pyridyl)-2-propen-1-one and cyclopentadiene. Tetrahedron 2002. [DOI: 10.1016/s0040-4020(02)00072-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Sensato FR, Cass QB, Longo E, Zukerman-Schpector J, Custodio R, Andrés J, Hernandes MZ, Longo RL. Molecular structure of the molybdenum oxo-diperoxo compound MoO(O(2))(2)(OPy)(H(2)O): a computational and X-ray study. Inorg Chem 2001; 40:6022-5. [PMID: 11681920 DOI: 10.1021/ic010020h] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have carried out a combined experimental and theoretical study of the molecular structure of the MoO(O(2))(2)(OPy)(H(2)O) coordination compound using X-ray crystallography and DFT-B3LYP computational method, respectively. The MoO(O(2))(2)(OPy)(H(2)O) complex crystallizes in the orthorhombic space group Pmna with Z = 4, a = 6.9001(9) A, b = 8.0471(1) A, c = 16.227(2) A, V = 901.0(2) A(3), and the X-ray data analysis yields a bipyramidal-pentagonal coordination polyhedron for the Mo atom. The pyridine N-oxide (OPy) ligand occupies the equatorial position, with the oxygen atom of this ligand being located in the same plane as the four peroxo oxygen atoms. The H(2)O ligand is situated trans to the oxo group, forming intermolecular hydrogen bonds with peroxo groups belonging to two adjacent complexes. In our theoretical approach these intermolecular interactions were taken into account by including two methanol molecules which form hydrogen bonds with the water ligand leading to a good agreement between the calculated and the experimental geometry. Our results suggest that it is necessary to take into account the presence of these interactions in order to reconcile the theoretical results to the experimental data, in particular the distance between Mo and the oxygen of water ligand. These results seem to be a general feature for analogous bis-peroxo complexes that have been reported in the literature.
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Llusar R, Beltrán A, Andrés J, Fuster F, Silvi B. Topological Analysis of Multiple Metal−Metal Bonds in Dimers of the M2(Formamidinate)4Type with M = Nb, Mo, Tc, Ru, Rh, and Pd. J Phys Chem A 2001. [DOI: 10.1021/jp011906+] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Domingo LR, Oliva M, Andrés J. A theoretical study of the reaction between cyclopentadiene and protonated imine derivatives: a shift from a concerted to a stepwise molecular mechanism. J Org Chem 2001; 66:6151-7. [PMID: 11529744 DOI: 10.1021/jo0015422] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction between cyclopentadiene and protonated pyridine-2-carboxaldehyde imine derivatives has been studied by using Hartree-Fock (HF) and B3LYP methods together with the 6-31G basis set. The molecular mechanism is stepwise along an inverted energy profile. This results from the protonation on both nitrogen atoms of the imine group and the pyridine framework. The first step corresponds to the nucleophilic attack of cyclopentadiene on the electron-poor carbon atom of the iminium cation group to give an acyclic cation intermediate, and the second step is associated with the ring closure of this intermediate via the formation of a C-N single bond yielding the final cycloadduct. Two reactive channels have been characterized corresponding to the endo and exo approach modes of the cyclopentadiene to the iminium cation. The role of the pyridium cation substituent and the nitrogen position (ortho, meta, and para) along the reaction pathway has been also considered. Solvent effects (dichloromethane) by means of a continuum model have been taken into account to model the experimental environment.
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Orellana C, Martínez F, Badía L, Millán JM, Montero MR, Andrés J, Prieto F. Trisomy rescue by postzygotic unbalanced (X;14) translocation in a girl with dysmorphic features. Clin Genet 2001; 60:206-11. [PMID: 11595022 DOI: 10.1034/j.1399-0004.2001.600306.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In this report we present the clinical features and molecular and cytogenetic findings in a female with partial trisomy 14q. Molecular and cytogenetic studies allowed us to determine that the extra 14q material (of paternal origin) was translocated postzygotically onto the maternal X chromosome. Consequently, only the derivative X chromosome was inactivated, although inactivation apparently did not spread over the entire chromosome 14q. This partial inactivation makes the present case unusual, giving rise to phenotypic features absent in other patients with partial trisomy 14q, typically restricted to the distal part of the chromosome.
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Andrés J, Canle L. M, Garcı́a M, Rodrı́guez Vázquez L, Santaballa J. A B3LYP/6-31G** study on the chlorination of ammonia by hypochlorous acid. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)00579-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Domingo L, Oliva M, Andrés J. A PM3 study of the molecular mechanism for the cycloaddition between cyclopentadiene and protonated pyridine-imine derivatives. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0166-1280(01)00370-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Sensato F, Treu Filho O, Longo E, Sambrano J, Andrés J. Theoretical analysis of the energy levels induced by oxygen vacancies and the doping process (Co, Cu and Zn) on SnO 2 (110) surface models. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s0166-1280(00)00731-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Calatayud M, Andrés J, Beltrán A, Silvi B. The hierarchy of localization basins: a tool for the understanding of chemical bonding exemplified by the analysis of the VO x and VO x + ( x =1-4) systems. Theor Chem Acc 2001. [DOI: 10.1007/s002140000241] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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50
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Castillo R, Andrés J, Moliner V. Quantum Mechanical/Molecular Mechanical Study on the Favorskii Rearrangement in Aqueous Media. J Phys Chem B 2001. [DOI: 10.1021/jp003264g] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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