and vibrational frequency computations (ωB97X-D4/def2-SVP/CPCM(Toluene)) for the conformers, some patterns became clear, see Table for binding energies and free energies of the most stable conformers. The corresponding structures for these lowest-energy dimers are presented in Figure . First of all, the dimers that contain nitrogen or sulfoxide tend to have larger binding energies than the molecules with sulfur, oxygen, or no heteroatoms.