Characterization of halogen···halogen interactions in crystalline dihalomethane compounds (CH2Cl2, CH2Br2 and CH2I2): a theoretical study.

A theoretical study was performed to examine halogen···halogen (X···X) bonds properties in crystalline dihalomethane CH2X2 compounds (X=Cl, Br and I). MP2/aug-cc-pVTZ calculations reveal that the interaction energies for CH2X2 dimers lie in the range between -3.7 and -9.9 kJ mol(-1). One of the most important results of this study is that, according to symmetry-adapted perturbation theory, the X···X interactions are largely dependent on dispersion interactions. The contribution of electrostatic energy in the X···X interaction increases in the order Cl < Br < I, which is consistent with the greater amount of positive electrostatic potential on the halogen atom.