Correlations between Computation and Experimental Thermodynamics of Halogen Bonding

Correlations between experimental, solution-phase thermodynamic data and calculated gas-phase energies of interaction are investigated for noncovalent halogen bonding interactions between electron-deficient iodo compounds and Lewis bases. The experimental data consist of free energies of interaction spanning roughly 7 kcal/mol; they encompass halogen bonds involving both organic (iodoperfluoroarene or iodoperfluoroalkane) and inorganic (I-2, IBr, ICN) donors with nitrogen- and oxygen-based acceptors and are divided into two sets according to the identity of the solvent in which they were determined (alkanes or CCl4). Adiabatic energies of halogen bonding were calculated using a variety of methods, including 22 DFT exchange-correlation fimctionals, using geometries optimized at the MP2/6-31+G(d,p) level of theory. Certain DFT functionals, particularly the B97-1, B97-2, and B98 family, provide outstanding linear correlations with the experimental thermodynamic data, as assessed by a variety of statistical methods.