Radial Potential Energy Functions of Linear Halogen-Bonded Complexes YX•••ClF (YX = FB, OC, SC, N2) and the Effects of Substituting X by Second-Row Analogues: Mulliken Inner and Outer Complexes

Energies of linear, halogen-bonded complexes in the isoelectronic series YX center dot center dot center dot ClF (YX = FB, OC, or N-2) are calculated at several levels of theory as a function of the intermolecular distance r(X center dot center dot center dot Cl) to yield radial potential energy functions. When YX = OC, a secondary minimum is observed corresponding to lengthened and shortened distances r(ClF) and r(CCl), respectively, relative to the primary minimum, suggesting a significant contribution from the Mulliken inner complex structure [O = C-Cl](+)center dot center dot center dot F-. A conventional weak, halogen-bond complex OC center dot center dot center dot ClF occurs at the primary minimum. For YX = FB, the primary minimum corresponds to the inner complex [F.B-Cl](+)center dot center dot center dot F-, while the outer complex FB center dot center dot center dot ClF is at the secondary minimum. The effects on the potential energy function of systematic substitution of Y and X by second-row congeners and of reversing the order of X and Y are also investigated. Symmetry-adapted perturbation theory and natural population analyses are applied to further understand the nature of the various halogen-bond interactions.

Automated summary

This article calculates the energies of linear, halogen-bonded complexes in the isoelectronic series YX ··· ClF. The radial potential energy functions are obtained as a function of the intermolecular distance. The effects of systematic substitution and reversal of the order of the constituents are also investigated. Symmetry-adapted perturbation theory and natural population analyses are applied to understand the nature of the halogen-bond interactions.