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Mata I.,CSIC - Institute of Materials Science | Alkorta I.,Institute Quimica Medica IQM CSIC | Molins E.,CSIC - Institute of Materials Science | Espinosa E.,CNRS Laboratory of Crystallography, Nuclear Magnetic Resonance and Modelling
Chemistry - A European Journal | Year: 2010

Topological analyses of the theoretically calculated electron densities for a large set of 163 hydrogenbonded complexes show that H··· X interactions can be classified in families according to X (X=atom or π orbital). Each family is characterised by a set of intrinsic dependencies between the topological and energetic properties of the electron density at the hydrogenbond critical point, as well as between each of them and the bonding distance. Comparing different atom-acceptor families, these dependencies are classified as a function of the van der Waals radius rX or the electronegativity χX, which can be explained in terms of the molecular orbitals involved in the interaction. According to this ordering, the increase of χX leads to a larger range of H···X distances for which the interaction is of pure closed-shell type. Same dependencies observed for H···O interactions experimentally characterised by means of high-resolution X-ray diffraction data show a good agreement with those obtained from theoretical calculations, in spite of a larger dispersion of values around the expected fitting functions in the experimental case. Theoretical dependencies can thus be applied to the analysis of the experimental electron density for detecting either unconventional hydrogen bonds or problems in the modelling of the experimental electron density. © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim. Source


Mata I.,CSIC - Institute of Materials Science | Alkorta I.,Institute Quimica Medica IQM CSIC | Espinosa E.,CNRS Laboratory of Crystallography, Nuclear Magnetic Resonance and Modelling | Molins E.,CSIC - Institute of Materials Science
Chemical Physics Letters | Year: 2011

The hydrogen bond interaction energy (EHB) of HF⋯HR (R = H, Li, Al, Cl, CCH) complexes under external electric fields is investigated in terms of the bonding distance and of several properties at the bond critical point. All these properties can be used for the estimation of EHB, being the positive curvature along the hydrogen bond path the most suited for the application to experimental electron densities. © 2011 Elsevier B.V. All rights reserved. Source


Bauza A.,University of the Balearic Islands | Alkorta I.,Institute Quimica Medica IQM CSIC | Frontera A.,University of the Balearic Islands | Elguero J.,Institute Quimica Medica IQM CSIC
Journal of Chemical Theory and Computation | Year: 2013

In this article, we report a comprehensive theoretical study of halogen, chalcogen, and pnicogen bonding interactions using a large set of pure and hybrid functionals and some ab initio methods. We have observed that the pure and some hybrid functionals largely overestimate the interaction energies when the donor atom is anionic (Cl- or Br-), especially in the halogen bonding complexes. To evaluate the reliability of the different DFT (BP86, BP86-D3, BLYP, BLYP-D3, B3LYP, B97-D, B97-D3, PBE0, HSE06, APFD, and M06-2X) and ab initio (MP2, RI-MP2, and HF) methods, we have compared the binding energies and equilibrium distances to those obtained using the CCSD(T)/aug-cc-pVTZ level of theory, as reference. The addition of the latest available correction for dispersion (D3) to pure functionals is not recommended for the calculation of halogen, chalcogen, and pnicogen complexes with anions, since it further contributes to the overestimation of the binding energies. In addition, in chalcogen bonding interactions, we have studied how the hybridization of the chalcogen atom influences the interaction energies. © 2013 American Chemical Society. Source


Alkorta I.,Institute Quimica Medica IQM CSIC | Elguero J.,Institute Quimica Medica IQM CSIC | Mo O.,Autonomous University of Madrid | Yanez M.,Autonomous University of Madrid | Del Bene J.E.,Youngstown State University
Physical Chemistry Chemical Physics | Year: 2015

Ab initio MP2/aug′-cc-pVTZ calculations have been carried out to investigate the structures, binding energies, and bonding characteristics of binary complexes HFBe:FCl, R2Be:FCl, and FCl:N-base, and of ternary complexes HFBe:FCl:N-base and R2Be:FCl:N-base for R = H, F, Cl; N-base = NH3, NHCH2, NCH. Dramatic synergistic cooperative effects have been found between the Be⋯F beryllium bonds and the Cl⋯N halogen bonds in ternary complexes. The Cl⋯N traditional halogen bonds and the Be⋯F beryllium bonds in binary complexes become significantly stronger in ternary complexes, while the F-Cl bond weakens. Charge-transfer from F to the empty p(σ) orbital of Be leads to a bending of the XYBe molecule and a change in the hybridization of Be, which in the limit becomes sp2. As a function of the intrinsic basicity of the nitrogen base and the intrinsic acidity of the Be derivative, the halogen-bond type evolves from traditional to chlorine-shared to ion-pair bonds. The mechanism by which an ion-pair complex is formed is similar to that involved in the dissociative proton attachment process. EOM-CCSD spin-spin coupling constants 1XJ(Cl-N) across the halogen bond in these complexes also provide evidence of the same evolution of the halogen-bond type. © the Owner Societies 2015. Source


Del Bene J.E.,Youngstown State University | Alkorta I.,Institute Quimica Medica IQM CSIC | Elguero J.,Institute Quimica Medica IQM CSIC
Journal of Physical Chemistry A | Year: 2014

Ab initio MP2/aug′-cc-pVTZ calculations have been carried out in search of equilibrium structures with P⋯Cl pnicogen bonds or halogen bonds on the potential energy surfaces H2FP:ClY for Y = F, NC, Cl, CN, CCH, CH3, and H. Three different types of halogen-bonded complexes with traditional, chlorine-shared, and ion-pair bonds have been identified. Two different pnicogen-bonded complexes have also been found on these surfaces. The most electronegative substituents F and NC form only halogen-bonded complexes, while the most electropositive substituents CH 3 and H form only pnicogen-bonded complexes. The halogen-bonded complexes involving the less electronegative groups Cl and CN are more stable than the corresponding pnicogen-bonded complexes, while the pnicogen-bonded complexes with CCH are more stable than the corresponding halogen-bonded complex. Traditional halogen-bonded complexes are stabilized by charge transfer from the P lone pair to the Cl-A σ* orbital, where A is the atom of Y directly bonded to Cl. Charge transfer from the Cl lone pair to the P-F σ* orbital stabilizes pnicogen-bonded complexes. As a result, the H2FP unit becomes positively charged in halogen-bonded complexes and negatively charged in pnicogen-bonded complexes. Spin-spin coupling constants 1XJ(P-Cl) for complexes with traditional halogen bonds increase with decreasing P-Cl distance, reach a maximum value for complexes with chlorine-shared halogen bonds, and then decrease and change sign when the bond is an ion-pair bond. 1pJ(P-Cl) coupling constants across pnicogen bonds tend to increase with decreasing P-Cl distance. © 2014 American Chemical Society. Source

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