Substituent Effects in Multivalent Halogen Bonding Complexes: A Combined Theoretical and Crystallographic Study.

In this manuscript, we combined ab initio calculations (RI-MP2/def2-TZVPD level of theory) and a search in the CSD (Cambridge Structural Database) to analyze the influence of aromatic substitution in charge-assisted multivalent halogen bonding complexes. We used a series of benzene substituted iodine derivatives C₆H₄(IF₄)Y (Y = H, NH₂, OCH₃, F, CN, and CF₃) as Lewis acids and used Cl- as electron rich interacting atoms. We have represented the Hammett's plot and observed a good regression coefficient (interaction energies vs. Hammett's σ parameter). Additionally, we demonstrated the direct correlation between the Hammett's σ parameter and the value of molecular electrostatic potential measured at the I atom on the extension of the C-I bond. Furthermore, we have carried out AIM (atoms in molecules) and NBO (natural bonding orbital) analyses to further describe and characterize the interactions described herein. Finally, we have carried out a search in the CSD (Cambridge Structural Database) and found several X-ray structures where these interactions are present, thus giving reliability to the results derived from the calculations.