Nature of halogen bonding: A Study based on the topological analysis of the Laplacian of electron charge density and an Energetic Decomposition Analysis.

DARÍO J. R. DUARTE; GLADIS L. SOSA; NÉLIDA M. PERUCHENA

Riviera Maya

Congreso; XXXVII Congreso de Químicos Teóricos de Expresión Latina - QUITEL 2011; 2011

In recent years, there has been an increasing interest in halogen bonds because of their unique properties and its tremendous potential in the development of new pharmaceutical compounds and materials. The study of nature of halogen bonding interactions has turned to be an important aspect of this topic. In this work we investigate the interactions of substituted ammonium [NHn(X3-n) (n= 0, 1, 2, 3 and X= -CH3, -F] with F-Cl molecule to ascertain the effects of various substituents upon the nature of these interactions. The intermolecular distribution of both the electronic charge density and that the function L(r)= -¼Ñ2r(r) has been studied within the framework of the atoms in molecules (AIM) theory, and the intermolecular interaction energies of the complexes have been analyzed using the reduced variational space (RVS) method. The MØller-Plesset [MP2/6-311++G(2d,2p)] calculations indicate that the binding energies for these complexes lie in the range between -1.27 kcal/mol (F-Cl···NF3) and -27.62 kcal/mol [F-Cl···N(NH3)3]. The topological analysis of the function L(r) reveals that the local topological properties measured on the critical point (3,+1) are good descriptors of the strength of these complexes. In addition, the results obtained using the RVS method 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-whitdrawing capacity, the electrostatic interaction between the electron cloud of the Lewis base and unprotected nucleus of the halogen atom of the Lewis acid, leads to the formation and determines the geometry of halogen bonds.