Probing Non-Covalent Interactions through Molecular Balances: A REG-IQA Study.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Interactions

Background:

• Molecular balances are designed to study specific chemical interactions.
• Understanding carbonyl-carbonyl interactions is crucial in various chemical contexts.
• Traditional geometric assumptions for molecular balances may not reflect lowest energy states.

Purpose of the Study:

• To analyze interaction energies in two series of molecular balances.
• To investigate the role of functional groups (X and Y) in carbonyl-carbonyl interactions.
• To evaluate the effectiveness of the Relative Energy Gradient-Interacting Quantum Atoms/Fragments (REG-IQA/IQF) method for predicting molecular behavior.

Main Methods:

• Utilized B3LYP/6-311++G(d,p)-D3 level of theory for energy calculations.
• Employed the energy partitioning method of Interacting Quantum Atoms/Fragments (IQA/IQF).
• Applied the Relative Energy Gradient (REG) method to correlate partitioned energies with total system energy.

Main Results:

• Identified that traditional 'open' and 'closed' conformations do not always represent the lowest energy states.
• Observed distinct behaviors between 1-H/1-OMe and 1-Me/1-NMe2 balances due to electrostatic and steric effects.
• Found that polarization, charge-transfer, and de-pyramidalization of the amide nitrogen influence closed conformer formation.
• Exchange-correlation energies become dominant over electrostatics in 2-Y balances, correlating with inductive effects.

Conclusions:

• The REG-IQA/IQF method provides atomistic insights into molecular balance energetics.
• Functional group identity critically impacts carbonyl-carbonyl interaction energies and conformational preferences.
• Computational methods like REG-IQA/IQF can aid in the experimental design and fine-tuning of molecular balances.