Using dispersion-corrected density functional theory to understand supramolecular binding thermodynamics.

Area of Science:

• Computational Chemistry
• Supramolecular Chemistry
• Physical Chemistry

Background:

• Accurate calculation of binding constants is essential for understanding supramolecular chemistry.
• Previous theoretical methods have limitations in predicting complex interaction energies.
• Dispersion-corrected density functional theory (DFT-D3) offers a promising approach.

Purpose of the Study:

• To illustrate and validate a theoretical approach for calculating equilibrium free energies of association.
• To assess the accuracy of the DFT-D3 method against experimental binding constants for new supramolecular complexes.
• To evaluate the reliability of the method for routine calculations of complex structures and energies.

Main Methods:

• Application of a nondynamic structure model using dispersion-corrected density functional theory (DFT-D3).
• Calculation of equilibrium free energies of association for eight new supramolecular complexes.
• Comparison of calculated binding constants (ΔGa) with experimentally determined values.

Main Results:

• The theoretical approach demonstrated good accuracy, with a mean deviation of 0.4 kcal mol(-1) and mean absolute deviation of 1.8 kcal mol(-1) from experimental data.
• Outliers were identified where computed solvation free energies contributed significantly to the error.
• The method achieves good to high accuracy (5-10% relative errors) for interaction energies of complexes up to 200-300 atoms.

Conclusions:

• The DFT-D3 based theoretical approach provides a reliable and accurate method for calculating supramolecular complex association energies.
• The method is suitable for routine computation of structures and gas phase interaction energies for moderately sized complexes.
• Further refinement in solvation energy calculations could improve accuracy for specific systems.