Solvation Free Energies for Aqueous and Nonaqueous Solutions Computed Using PM7 Atomic Charges

Area of Science:

• Computational chemistry
• Physical chemistry
• Chemical thermodynamics

Background:

• Calculating solvation free energies (ΔGsolv°) is crucial for understanding chemical processes in solution.
• Accurate prediction of solvation energies is essential for drug design and materials science.
• Existing methods can be computationally intensive or lack accuracy across diverse solvent types.

Purpose of the Study:

• To develop a simple, accurate, and efficient method for calculating solvation free energies.
• To validate the ESE-PM7 method across a wide range of solvents and solutes.
• To provide a tool for rapid screening of solvation free energies in complex molecular systems.

Main Methods:

• Utilized a noniterative Conductor-like Screening Model (COSMO) algorithm.
• Employed molecular geometries and atomic charges derived from the semiempirical PM7 method.
• Validated the method against experimental data for 92 solvents and 988 solutes.

Main Results:

• Achieved mean absolute errors (MAEs) of 1.62 kcal/mol for neutral solutes and 3.06 kcal/mol for ions in aqueous solutions.
• Reported MAEs of 0.97, 0.74, and 0.51 kcal/mol for neutral molecules in polar protic, polar aprotic, and nonpolar organic solvents, respectively.
• Demonstrated high accuracy and broad applicability across diverse chemical environments.

Conclusions:

• The ESE-PM7 method offers a robust and computationally inexpensive approach for solvation free energy calculations.
• The method's accuracy and efficiency make it suitable for screening large molecular systems, including pharmaceuticals and biological molecules.
• ESE-PM7 provides a valuable tool for researchers in computational chemistry, drug discovery, and materials science.