Analyzing the Energetics of the Four Aromatic Ring Interactions: Theoretical Study

Area of Science:

• Supramolecular Chemistry
• Computational Chemistry
• Physical Chemistry

Background:

• Noncovalent interactions, particularly π-π and C-H···π types, are crucial in various scientific fields but remain poorly understood.
• A clear understanding of their intensity, geometry, energetics, and physical principles is lacking.

Purpose of the Study:

• To investigate the nature and stability of noncovalent interactions in dimers of four fused aromatic rings (4FARs): Benz[a]anthracene, Chrysene, Tetracene, and Triphenylene.
• To elucidate the factors governing the stability and preferred configurations of these homodimer complexes.

Main Methods:

• Utilized theoretical computations including Interaction Energy (IE) and Stabilization Energy (E_SAPT).
• Employed frontier orbital gaps, aromaticity indices (FLU, PDI, HOMA, PLR), and real-space analyses (QTAIM, NCI).
• Incorporated crystal-topology descriptors like Hirshfeld surfaces and 2D fingerprints.

Main Results:

• Found a weak correlation between interaction/stabilization energies and HOMO-LUMO gaps or Clar's π sextet rule.
• Aromaticity, QTAIM, NCI, and Hirshfeld analyses showed agreement with interaction energies, highlighting their importance.
• Identified cross-conformers as more stable than face-conformers, with Tet exhibiting the most stable linear geometry and Tri the least stable compact geometry.

Conclusions:

• The study clarifies the complex interplay of factors governing noncovalent interactions in 4FAR systems.
• Emphasizes the critical role of π-π stacking in stabilizing these homodimer complexes.
• Provides insights into predicting and understanding noncovalent interactions in complex molecular systems.