Table 6. Binding Energies Calculated at the MP2/aug-cc-pVDZ(PP) and MP2/aug-cc-pVTZ(PP) Levels of Theory for F-I-X₄···π-System Complexes (Where X = F, Cl, Br, and I; π-System = Benzene (BZN) and Hexafluorobenzene (HFB)) at the Most Favorable I···π-System Distance.

complex	F-I-X4···BZN			F-I-X4···HFB
X4	bond lengtha (Å)	EMP2/aug-cc-pVDZb (kcal/mol)	EMP2/aug-cc-pVTZb (kcal/mol)	bond lengtha (Å)	EMP2/aug-cc-pVDZb (kcal/mol)	EMP2/aug-cc-pVTZb (kcal/mol)
F4	3.11	–10.67	–12.38	3.33	–2.04	–3.06
Cl4	3.10	–14.20	–16.39	3.21	–7.04	–8.91
Br4	3.14	–14.54	–16.95	3.26	–7.99	–10.10
I4	3.18	–15.01	–17.79	3.36	–8.38	–10.87

^aThe most favorable F-I-X₄···π-system distance based on PES scan illustrated in Figure 8.

^bPP functions were added to Br and I atoms.