A theoretical investigation of the characteristics of hydrogen/halogen bonding interactions in dibromo-nitroaniline.

In this work, computations of density functional theory (DFT) were carried out to investigate the nature of interactions in solid 2,6-dibromo-4-nitroaniline (DBNA). This system was selected to mimic the hydrogen/halogen bonding found within crystal structures as well as within biological molecules. DFT (M06-2X/6-311++G**) calculations indicated that the binding energies for different of interactions lie in the range between -1.66 and -9.77 kcal mol(-1). The quantum theory of atoms in molecules (QTAIM) was applied to provide more insight into the nature of these interactions. Symmetry-adapted perturbation theory (SAPT) analysis indicated that stability of the Br···Br halogen bonds is predicted to be attributable mainly to dispersion, while electrostatic forces, which have been widely believed to be responsible for these types of interactions, play a smaller role. Our results indicate that, for those nuclei participating in hydrogen/halogen bonding interactions, nuclear quadrupole resonance parameters exhibit considerable changes on going from the isolated molecule model to crystalline DBNA.