Polar flattening and the strength of halogen bonding.

The effect of polar flattening on the stability of 32 halogen-bonded complexes was investigated by utilizing CCSD(T)/CBS, DFT, and DFT-SAPT/CBS methods. It is shown that the value of polar flattening increases with the decreasing value of studied isodensity. For the complexes investigated, the polar flattening based on the isodensity of 0.001 au reaches 0.2-0.3 Å and 10-15% in absolute and relative values, respectively. These geometrical changes induce differences in the stabilization energy up to 20%.