Molecular aniline clusters. I. The electronic ground state.

Area of Science:

• Computational Chemistry
• Molecular Interactions
• Quantum Chemistry

Background:

• Aniline is a fundamental aromatic amine with significant industrial applications.
• Understanding the aggregation behavior of aniline is crucial for predicting its physical and chemical properties.
• Previous studies on aniline clusters have been limited in scope and computational rigor.

Purpose of the Study:

• To determine the most stable structures of the aniline dimer and trimer in their electronic ground state.
• To elucidate the nature and magnitude of intermolecular forces governing aniline aggregation.
• To compare the interaction energies and bonding characteristics of aniline clusters with those of benzene.

Main Methods:

• Global optimization techniques applied to a model potential, refined with *ab initio* calculations (spin-component-scaled LMP2).
• Density Functional Theory Symmetry Adapted Perturbation Theory (DFT-SAPT) for detailed interaction energy analysis.
• Systematic search of the potential energy surface for low-lying minima.

Main Results:

• The most stable aniline dimer adopts a head-to-tail configuration with equivalent monomers.
• Van der Waals dispersion is the dominant interaction in the dimer, comparable to benzene but with a larger total interaction energy.
• The global minimum for the trimer features a hydrogen-bonding network of three directional NH-N bonds, with distinct monomers.
• Nonadditive three-body dispersion effects were found to be minor in the trimer.

Conclusions:

• The aniline dimer's stability is primarily driven by dispersion forces, exceeding that of the benzene dimer.
• The aniline trimer's structure is dictated by strong hydrogen bonding interactions.
• These findings provide critical insights into the self-assembly and properties of aniline in condensed phases.