Nature of the water/aromatic parallel alignment interactions

Area of Science:

• Computational Chemistry
• Molecular Interactions
• Physical Chemistry

Background:

• Water and aromatic molecules are ubiquitous in chemical and biological systems.
• Understanding non-covalent interactions is crucial for molecular recognition and complex formation.
• Previous studies focused on other water-aromatic interactions, leaving parallel alignment less explored.

Purpose of the Study:

• To investigate the nature and strength of water/aromatic parallel alignment interactions.
• To elucidate the energetic contributions and electronic characteristics of these interactions.
• To compare parallel alignment interactions with other known water-aromatic interactions.

Main Methods:

• High-level quantum chemical calculations, including coupled-cluster theory with single, double, and perturbative triple excitations (CCSD(T)).
• Energy decomposition analysis (EDA) to dissect interaction energies.
• Symmetry-adapted perturbation theory (SAPT) and Natural Orbitals for Chemical Valence (NOCV) for detailed electronic analysis.

Main Results:

• Significant interaction energies were calculated, reaching up to -2.45 kcal mol⁻¹.
• Electrostatic interactions dominate at large horizontal displacements, while dispersion forces are key at small displacements.
• Charge transfer (π → σ*(O-H)) was identified as a contributing factor in strong interactions.

Conclusions:

• Water/aromatic parallel alignment interactions are a notable non-covalent force.
• The interplay of electrostatic and dispersion forces governs the strength and nature of these interactions.
• These findings enhance our understanding of molecular interactions in systems containing water and aromatic moieties.