3.2.2 | Interaction Energies
There are five different types of intermolecular noncovalent interactions in the six diiodoalkene dimers (see Figure 4): I…I, I…O, I…C(π), I…H and O…O. Interaction energy is an importantmeasure of the strength of an intermolecular interaction. The interaction energy in the dimers can be regarded as the energy difference between the dimer and the monomers as captured via Eq. (1). Table 4 summarizes the interaction energies of the halogen bonds in the six dimers. All results were corrected for BSSE by using counterpoise methods. Naturally, the effect of BSSE correction is prominent for halogen bonds. Calculations are carried out for crystal and optimized dimers, respectively, to explore whether if it is necessary to optimize the crystal structure geometries.