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Updated: Aug 13, 2025
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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
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The Halogen Bond in Weakly Bonded Complexes and the Consequences for Aromaticity and Spin-Orbit Coupling
Ana V Cunha1, Remco W A Havenith2,3, Jari van Gog1
1MolSpec, Departement Chemie, Universiteit Antwerpen, Groenenborgerlaan 171, 2020 Antwerpen, Belgium.
Molecules (Basel, Switzerland)
|January 21, 2023
Summary
This study investigates halogen bonds between fluorinated compounds and aromatic rings, finding interaction strength increases with halogen size (Cl < Br < I). Aromaticity remains intact, but spin-orbit coupling increases, potentially affecting intersystem crossing rates.
Area of Science:
- Computational Chemistry
- Supramolecular Chemistry
- Chemical Physics
Background:
- Halogen bonding is a key non-covalent interaction.
- Understanding factors governing halogen bond strength is crucial for molecular design.
- Aromatic systems are common motifs in biologically relevant molecules.
Purpose of the Study:
- To investigate halogen bond complexes (CF3X⋯Y and C2F3X⋯Y) involving aromatic rings (Y = furan, thiophene, selenophene) and halogens (X = Cl, Br, I).
- To determine the factors influencing the interaction between the halogen atom and the aromatic ring.
- To assess the impact of halogen bonding on the aromaticity and electronic properties of the ring.
Main Methods:
- Density Functional Theory (DFT) calculations, specifically PBE0-dDsC/QZ4P.
- Coupled-Cluster with Singles and Doubles and perturbative Doubles (CCSD(T)) calculations for benchmarking.
- Experimental data comparison.
- Energy Decomposition Analysis (EDA).
Main Results:
- PBE0-dDsC/QZ4P provides an adequate description of interaction energies compared to CCSD(T) and experimental results.
- Halogen bond interaction with π-bonds in perpendicular orientation is stronger than with in-plane lone pairs.
- Interaction strength follows the trend Cl < Br < I; chalcogenide identity and C-X bond hybridization are not decisive.
- Electrostatic, orbital, and dispersion interactions contribute significantly to the total interaction energy without one factor dominating.
- Aromaticity and π-ring current remain undisturbed upon halogen bond formation.
- Spin-orbit coupling increases, suggesting faster intersystem crossing.
Conclusions:
- The strength of halogen bonds in these systems is primarily governed by the halogen atom's size.
- Halogen bond formation does not disrupt the inherent aromaticity of the ring system.
- Increased spin-orbit coupling upon halogen bond formation may influence photophysical properties through enhanced intersystem crossing.
Keywords:
density functional theoryenergy decomposition analysishalogen bondsring current analysisspin-orbit couplingMore Related Videos
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