Antonio Vila

Bio: Antonio Vila is an academic researcher from University of Vigo. The author has contributed to research in topics: Atoms in molecules & Hydrogen bond. The author has an hindex of 15, co-authored 29 publications receiving 555 citations.

Atoms in molecules interpretation of the anomeric effect in the O ? C ? O unit

Abstract: The conformational preferences of two model compounds for the OCH2O anomeric unit: methanediol and dimethoxymethane analyzed within the framework of the QTAIM theory provide a new interpretation of the anomeric effect. The characteristic stabilization of the gauche conformers of these compounds is accompanied by a progressive reduction of the electron population of the hydrogens of the central methylene as the number of their gauche interactions to lone pairs rises. The electron population removed from these atoms during the conformational change is gained in the gauche conformers by atoms of larger atomic number, which results in a more negative molecular energy. Also, the variations displayed by atomic populations and the QTAIM delocalization indexes are not keeping in line with the hyperconjugative model of the anomeric effect. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007

Topological characterisation of intermolecular lithium bonding

Abstract: Bader’s atoms in molecules topological theory was employed to analyse the B3LYP/6-311++G(3d2f,3p2d) electron distributions of several adducts that contain LiF. The results indicate significant differences between lithium bonding (LB) and hydrogen bonding (HB): (i) in spite of their larger stability, the charge density at the intermolecular critical points of LB complexes is about half of its value in the corresponding HB complexes, suggesting a dominant role of electrostatic interactions in the former; (ii) the Li atom in LB compounds is more shared between the base atom and the attached fluorine than hydrogen in HB complexes; and (iii) the Li atom gains electron charge from the hydrogens in all the complexes here studied, undergoing energetic stabilisation.

Transferability in alkyl monoethers. II. Methyl and methylene fragments

Abstract: The transferability of the atomic and bond properties of the methyl and methylene fragments in linear unbranched alkyl monoethers was studied using the Theory of Atoms in Molecules (AIM). This theory has been applied to the analysis of the HF/6-31++G**//HF/6-31G* electron charge distributions of a series of 33 dialkyl ethers, CH3(CH2)mO(CH2)nCH3, [n=0,1(n⩽m⩽9), n=2,3(n⩽m⩽8), n=4(n⩽m⩽5)]. The results obtained indicate that the methyl and methylene fragments situated in α, β, γ, or δ positions with respect to the oxygen atom are different to those of an n-alkane. Nevertheless, CH3 and CH2 at more distant positions can be considered as standard units, whose nonenergetic properties coincide with those of the corresponding fragment in an n-alkane. On the contrary, the energetic properties of the fragments maintain a differential value with respect to the n-alkane in all of the positions studied in the series. The properties of the methyl or methylene fragments in α to the oxygen depend on the size (methyl or l...

AIM study on the transferability of the oxygen atom in linear ethers

Abstract: The integrated values of the electron population, electron energy, nucleus–electron potential energy interaction, dipole moment and volume of the oxygen atoms, and the main properties of the O—C bo...

Electron density characterisation of intermolecular interactions in the formaldehyde dimer and trimer

Abstract: The electron density distributions of the diverse structures of formaldehyde dimer and trimer have been analysed within the framework of the atoms in molecules theory (AIM) with Dunning's correlation consistent basis sets aug-cc-pVXZ (X=D,T) at the B3LYP level. The angle of electrophilic attack as predicted by the Laplacian of the charge density gives a poor estimation of hydrogen bond angles in these clusters. The AIM integrated charges indicate that no charge transfer takes places between the constituent monomers in the planar clusters, whereas a sizeable flow of charge takes place in the non-planar complexes. The contribution of non-additive terms to the trimerisation energy is significant (it amounts more than 11% of the overall trimerisation energy).

Red- versus Blue-Shifting Hydrogen Bonds: Are There Fundamental Distinctions?

Abstract: The OH covalent bond of conventional hydrogen bonds of the OH···O type undergoes a lengthening as a result of the complex formation, and the OH stretching frequency shifts to the red; the same is t...

The UMIST database for astrochemistry 1999

Abstract: We report a new version of the UMIST database for astrochemistry. The previous (1995) version has been updated and its format has been revised. The database contains the rate coefficients, temperature ranges and – where available – the temperature dependence of 4113 gas-phase reactions important in astrophysical environments. The data involve 396 species and 12 elements. We have also tabulated permanent electric dipole moments of the neutral species and heats of formation. A new table lists the photo process cross sections (ionisation, dissociation, fragmentation) for a few species for which these quantities have been measured. Data for Deuterium fractionation are given in a separate table. Finally, a new online Java applet for data extraction has been created and its use is explained in detail. The detailed new datafiles and associated software are available on the World Wide Web at http://www.rate99.co.uk.

Influence of Hybridization and Substitution upon the Properties of the CH··O Hydrogen Bond

Abstract: Ab initio calculations are used to compare the hydrogen bonding ability of acetylene and ethylene, and various derivatives, with the analogous properties of alkanes. Water is used as the universal proton acceptor and paired with HCCH, FCCH, ClCCH, and NCH as well as with ethylene, and its mono-, di-, and trifluorosubstituted derivatives. With regard to the hydrocarbons, sp-hybridized acetylene forms the strongest bond, followed by sp2 and then sp3. Halogenation of the proton donor strengthens each type of hydrogen bond, particularly when the substitution takes place on the C involved in the hydrogen bond. sp3-hybridized systems are most sensitive to this substitution-induced bond strengthening, followed in order by sp2 and sp. For each hybridization type, the length of the hydrogen bond shortens in proportion to the strengthening, with alkanes exhibiting the greatest sensitivity and alkynes the least. Whereas formation of the hydrogen bond causes the sp3 CH bond to contract and undergo a blue shift, the o...

Anion Induced Formation of Supramolecular Associations Involving Lone pair−π and Anion−π Interactions in Co(II) Malonate Complexes: Experimental Observations, Hirshfeld Surface Analyses and DFT Studies

Abstract: Three Co(II)–malonate complexes, namely, (C5H7N2)4[Co(C3H2O4)2(H2O)2](NO3)2 (1), (C5H7N2)4[Co(C3H2O4)2(H2O)2](ClO4)2 (2), and (C5H7N2)4[Co(C3H2O4)2(H2O)2](PF6)2 (3) [C5H7N2 = protonated 2-aminopyridine, C3H4O4 = malonic acid, NO3– = nitrate, ClO4– = perchlorate, PF6– = hexafluorophosphate], have been synthesized from purely aqueous media, and their crystal structures have been determined by single crystal X-ray diffraction. A thorough analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions in 1–3, which are crucial in building supramolecular architectures. When these complexes are structurally compared with their previously reported analogous Ni(II) or Mg(II) compounds, a very interesting feature regarding the role of counteranions has emerged. This phenomenon can be best described as anion-induced formation of extended supramolecular networks of the type lone pair−π/π–π/π–anion−π/π–lone pair and lone pair−π/π–π/π–anion involving various weak forces lik...

Molecular dynamics simulation of swollen membrane of perfluorinated ionomer.

Abstract: Molecular dynamics simulations of the swollen membrane of perfluorinated ionomer, which is composed of poly(tetrafluoroethylene) backbones and perfluosulfonic pendant side chains, have been undertaken to analyze the static and dynamic properties of the water and the side chain in the membrane. The calculations were carried out for four different water contents, 5, 10, 20 and 40 wt %, at 358.15 K and 0.1MPa.The results are summarized as follows: (1) The sulfonic acid is the unique site to which water molecules can bind, and the other sites in the pendant side chain have no bound water even at high water concentration. (2) Sulfonic acids aggregate in the short range within 4.6−7.7 A despite the electrostatic repulsion between them. In such aggregates, a water molecule bridges two sulfonic acids. (3) Pendant side chains prefer to orient perpendicular to the hydrophilic/hydrophobic interface, and long-range correlation of side chain orientations is observed at 20 and 40 wt % water uptake membranes. (4) In a ...