Outline

  • Abstract
  • Keywords
  • Introduction
  • Method and Calculation Details
  • Results
  • Conclusions
  • Acknowledgments
  • Reference

رئوس مطالب

  • چکیده
  • کلید واژه ها
  • مقدمه
  • روش و جزئیات محاسبه
  • نتایج
  • نتیجه گیری

Abstract

In this work we investigate the nature of the Cl···N interactions in complexes formed between substituted ammonium [NHn (x3-n) n=0, 1, 2, 3 X=-CH3, -F] as Lewis bases and F−Cl molecule as Lewis acid. They have been chosen as a study case due to the wide range of variation of their binding energies, BEs. Møller-Plesset [MP2/6-311++G(2d,2p)] calculations show that the BEs for this set of complexes lie in the range from 1.27 kcal/mol [F – Cl…NF3] to 27.62 kcal/mol [inF – Cl…N(CH3)3]. The intermolecular distribution of the electronic charge density and their (L(r)=-1/4 ∇2 ρ(r function have been investigated within the framework of the atoms in molecules (AIM) theory. The intermolecular interaction energy decomposition has also been analyzed using the reduced variational space (RVS) method. The topological analysis of the L(r) function reveals that the local topological properties measured at the (3,+1) critical point [in L(r) topology] are good descriptors of the strength of the halogen bonding interactions. The results obtained from energy decomposition analysis indicate that electrostatic interactions play a key role in these halogen bonding interactions. These results allow us to establish that, when the halogen atom is bonded to a group with high electron-withdrawing capacity, the electrostatic interaction between the electron cloud of the Lewis base and the halogen atom unprotected nucleus of the Lewis acid produces the formation and determines the geometry of the halogen bonded complexes. In addition, a good linear relationship has been established between: the natural logarithm of the BEs and the electrostatic interaction energy between electron charge distribution of N atom and nucleus of Cl atom, denoted as Ve-n (N,Cl) within the AIM theory.

Keywords: - - - -

Conclusions

This work, carried out on a set of complexes within a wide range of variation of binding energy (from 1.27 to 27.62 kcal/ mol), highlights the utility of the topological analysis of the charge density and of the L(r) function, in conjunction with energy decomposition analysis as a methodology to investigate the nature of the halogen bonds. Based on the energy decomposition analysis, we have found that the electrostatic and the charge transference (in minor measure) components have the most significant contributions to the total interaction energy -in all ranges of strength- of the complexes analyzed here and play a substantial role in determining the optimal geometry of the complexes. The local properties at (3,-1) CPs in ρ(r) and (3,+1) CPs in L(r) topologies are good descriptors of the strength of these complexes. The local properties at (3,+1) CPs in L(r) topology reveal that, the strength of interaction increases with depletion of electronic charge density over the σ-hole.

Moreover, the topological analysis of the L(r) function reveals that the electronic density measured at the (3,+1) CP of the L(r) function is a good descriptor of the electrostatic component. Furthermore, a good lineal correlation was established between the ρ(rhole) and EES. In addition, a lineal relationship was established between the |Ve-n(N,Cl)| values and the natural logarithm of the binding energy. These findings suggest that, the electrostatic interaction between the lone pair of N atom and nucleus of Cl atom plays a key role in stabilizing these halogen bonding interactions.

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