Effect of direct and indirect exchange interactions on geometries and binding energies of molecular complexes. The dimer (CL2)2

Abstract

An analysis is made of the most stable geometry and the energy of interaction for the chlorine dimer, on the basis of a model which was previously used for interpreting hydrogen bonding in the dimers (HF)2 and (H2O)2 and the molecular complex HF⋅H2O. In the model, an analogy is assumed between the phenomenon of indirect exchange (’’superexchange’’) in ionic solids with paramagnetic cations and weak binding energies (≊1 kcal/mole) of molecular complexes. First-order exchange perturbation theory and an ’’effective-electron’’ description of the system are employed. The model predicts a nonplanar structure lacking a center of symmetry. The dimerization energy is estimated to lie between 1.4 and 2.0 kcal/mole. Agreement with experimental information is analyzed. We also briefly discuss the dimer (F2)2.