Halogen bonding of substituted iodobenzenes with potential solvent molecules: A comparison of binding energies

Results of a series of MP2 calculations on the halogen bonding interactions of a variety of oxygen and chlorine containing Lewis bases with iodobenzene, monofluoroiodobenzenes, pentafluoroiodobenzene, and p-iodophenol are reported. The O-containing bases, for the most part, gave binding energies that correlated with basicity, but there were exceptions. The calculated values for the binding energy were on the order of 1 kcal/mol for the Cl bases, but varied from 1 to 8 kcal/mol for 0 bases. The effect of higher order correlation effects (MP4 and CCSD) on the energies was relatively minor. Calculations using a PCM to simulate solvent showed that in all cases, this effect lowers the binding energy of the halogen bond even though the computed halogen bond distance decreased. This work also compared multiple binding sites on the p-iodophenol system in complexes with H2O; two hydrogen bonding, one it bonding, and the halogen bonding site to the iodine atom. It was found that although the halogen binding yields a significant BE of about 1-2 kcal/mol, this value is far below the hydrogen bonding sites. (C) 2012 Elsevier B.V. All rights reserved.