Intermolecular interaction between hexafluorobenzene and benzene: Ab initio calculations including CCSD(T) level...

Area of Science:

• Computational chemistry
• Molecular interactions
• Physical organic chemistry

Background:

• Understanding non-covalent interactions is crucial in chemistry.
• Aromatic systems like benzene and hexafluorobenzene are fundamental building blocks in organic chemistry.
• Quantifying interaction energies informs molecular design and predicts material properties.

Purpose of the Study:

• To calculate the intermolecular interaction energy of the hexafluorobenzene-benzene complex.
• To compare the stability of different complex orientations (slipped-parallel, sandwich, T-shaped).
• To elucidate the contributions of dispersion and electrostatic forces to the interaction.

Main Methods:

• Utilized the ARS-E model (formerly AIMI) for calculating interaction energies.
• Employed coupled cluster with singles and doubles and perturbative triples (CCSD(T)) calculations extrapolated to the basis-set limit.
• Estimated CCSD(T) energies using MP2 calculations and a correction term.

Main Results:

• The slipped-parallel (Cs) complex showed the largest interaction energy (-5.38 kcal/mol).
• The sandwich (C6v) complex was slightly less stable (-5.07 kcal/mol), while T-shaped complexes had minimal interaction energies.
• Dispersion forces were the primary attractive component, enhanced by stabilizing electrostatic interactions in the slipped-parallel hexafluorobenzene-benzene complex.

Conclusions:

• The slipped-parallel orientation is preferred for hexafluorobenzene-benzene complexes due to synergistic electrostatic and dispersion interactions.
• The calculated interaction energy is approximately double that of the benzene dimer.
• Dispersion forces play a key role in stabilizing these aromatic complexes, particularly in non-sandwich arrangements.