title: Traditional and ion-pair halogen-bonded complexes between chlorine and bromine derivatives and a nitrogen-heterocyclic carbene.
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.
authors.affiliation: Departamento de Ciencias Químicas, Facultad de Ciencias Exactas, Universidad Andres Bello , Av. Republica 275, Santiago, Chile.
authors.forename: Oscar
authors.initials: O
authors.lastname: Donoso-Tauda
authors.forename: Pablo
authors.initials: P
authors.lastname: Jaque
authors.forename: José
authors.initials: J
authors.lastname: Elguero
authors.forename: Ibon
authors.initials: I
authors.lastname: Alkorta
mesh_terms: D001966:Bromine / Q000737:chemistry*; D002713:Chlorine / Q000737:chemistry*; D004583:Electrons; D005461:Fluorine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D055672:Static Electricity; D013816:Thermodynamics
chemical_list: C030011:carbene; D005461:Fluorine; D002713:Chlorine; D008697:Methane; D001966:Bromine