The Halogen Bond in Weakly Bonded Complexes and the Consequences for Aromaticity and Spin-Orbit Coupling

Ana V. Cunha*, Remco W. A. Havenith, Jari van Gog, Freija De Vleeschouwer, Frank De Proft, Wouter Herrebout*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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The halogen bond complexes CF (Formula presented.) X⋯Y and C (Formula presented.) F (Formula presented.) X⋯Y, with Y = furan, thiophene, selenophene and X = Cl, Br, I, have been studied by using DFT and CCSD(T) in order to understand which factors govern the interaction between the halogen atom X and the aromatic ring. We found that PBE0-dDsC/QZ4P gives an adequate description of the interaction energies in these complexes, compared to CCSD(T) and experimental results. The interaction between the halogen atom X and the (Formula presented.) -bonds in perpendicular orientation is stronger than the interaction with the in-plane lone pairs of the heteroatom of the aromatic cycle. The strength of the interaction follows the trend Cl < Br < I; the chalcogenide in the aromatic ring nor the hybridization of the C–X bond play a decisive role. The energy decomposition analysis shows that the interaction energy is dominated by all three contributions, viz., the electrostatic, orbital, and dispersion interactions: not one factor dominates the interaction energy. The aromaticity of the ring is undisturbed upon halogen bond formation: the (Formula presented.) -ring current remains equally strong and diatropic in the complex as it is for the free aromatic ring. However, the spin-orbit coupling between the singlet and triplet (Formula presented.) states is increased upon halogen bond formation and a faster intersystem crossing between these states is therefore expected.

Original languageEnglish
Article number772
Number of pages14
Issue number2
Publication statusPublished - 12-Jan-2023


  • density functional theory
  • energy decomposition analysis
  • halogen bonds
  • ring current analysis
  • spin-orbit coupling

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