Analytical energy gradient for the second-order Møller-Plesset perturbation theory coupled with the reference...

Area of Science:

• Computational chemistry
• Physical chemistry
• Chemical reaction dynamics

Background:

• Solvatochromic shifts in activation free energies are crucial for controlling chemical reactions.
• Accurate prediction of these energies necessitates precise determination of stationary points along reaction pathways in solution.
• The Diels-Alder reaction is a fundamental organic transformation with significant synthetic applications.

Purpose of the Study:

• To develop and apply a computational method for accurately predicting activation free energies of reactions in solution.
• To investigate the efficacy of the second-order Møller-Plesset perturbation (MP2) theory combined with the reference interaction site model (RISM) for this purpose.
• To validate the computational approach against experimental data for a model Diels-Alder reaction.

Main Methods:

• Utilized the second-order Møller-Plesset perturbation (MP2) theory.
• Employed a fitting approach combined with the reference interaction site model (RISM) to determine the MP2 analytical energy gradient.
• Calculated coupled-cluster energy and thermal correction using MP2-optimized geometry, incorporating solvent effects.

Main Results:

• Successfully determined the MP2 analytical energy gradient for the reaction system.
• Calculated activation free energies for the Diels-Alder reaction between cyclopentadiene and methyl vinyl ketone.
• Achieved an accuracy within 2 kcal/mol compared to experimental values.

Conclusions:

• The combined MP2/RISM approach with the developed fitting method provides accurate predictions of activation free energies in solution.
• This computational strategy is effective for studying reaction mechanisms and controlling reaction outcomes.
• The method shows promise for broader applications in computational chemistry and reaction dynamics.