A theoretical investigation on the nature of Cl • • • N and Br • • • N halogen bonds in F-Ar-X • • • NCY complexes (X = Cl, Br and Y = H, F, Cl, Br, OH, NH2, CH3 and CN)

A theoretical study was performed to examine intermolecular halogen bonds interactions in F-Ar-X center dot center dot center dot NCY complexes (X = Cl, Br and Y = H, F, Cl, Br, OH, NH2, CH3 and CN). Examination of the electrostatic potentials of the NCY monomers indicates that the addition of substituents has a large influence upon the most negative electrostatic potential on the surface of the interacting nitrogen and thus modulates these halogen-bonding interactions. The calculated CCSD(T)/aug-cc-pVTZ interaction energies for the complexes span from -0.88 to -3.20 kcal/mol. The nature of Cl center dot center dot center dot N and Br center dot center dot center dot N interactions has been identified in terms of the bond critical point analysis within the quantum theory of atoms in molecules (QTAIM). According to energy decomposition analysis, the stabilities of the F-Ar-X center dot center dot center dot NCY interactions are predicted to be attributable mainly to electrostatic and polarization effects, while dispersion forces play a smaller role in stabilizing these complexes. (c) 2012 Elsevier B.V. All rights reserved.