Traditional and ion-pair halogen-bonded complexes between chlorine and bromine derivatives and a nitrogen-heterocyclic carbene

J Phys Chem A. 2014 Oct 9;118(40):9552-60. doi: 10.1021/jp506663x. Epub 2014 Sep 18.

Abstract

A theoretical study of the halogen-bonded complexes (A-X···C) formed between halogenated derivatives (A-X; A = F, Cl, Br, CN, CCH, CF3, CH3, H; and X = Cl, Br) and a nitrogen heterocyclic carbene, 1,3-dimethylimidazole-2-ylidene (MeIC) has been performed using MP2/aug'-cc-pVDZ level of theory. Two types of A-X:MeIC complexes, called here type-I and -II, were found and characterized. The first group is described by long C-X distances and small binding energies (8-54 kJ·mol(-1)). In general, these complexes show the traditional behavior of systems containing halogen-bonding interactions. The second type is characterized by short C-X distances and large binding energies (148-200 kJ·mol(-1)), and on the basis of the topological analysis of the electron density, they correspond to ion-pair halogen-bonded complexes. These complexes can be seen as the interaction between two charged fragments: A(-) and (+)[X-CIMe] with a high electrostatic contribution in the binding energy. The charge transfer between lone pair A(LP) to the σ* orbital of C-X bond is also identified as a significant stabilizing interaction in type-II complexes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bromine / chemistry*
  • Chlorine / chemistry*
  • Electrons*
  • Fluorine / chemistry*
  • Hydrogen Bonding
  • Methane / analogs & derivatives*
  • Methane / chemistry
  • Models, Chemical
  • Static Electricity
  • Thermodynamics

Substances

  • carbene
  • Fluorine
  • Chlorine
  • Methane
  • Bromine