KID Procedure Applied on the [(PY₅Me₂)MoO]⁺ Complex

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• The Koopmans in DFT (KID) protocol is typically used for closed-shell organic molecules.
• Evaluating reactivity descriptors in open-shell systems requires careful selection of density functionals.
• Conceptual Density Functional Theory (DFT) provides tools for understanding molecular reactivity.

Purpose of the Study:

• To adapt and apply the KID protocol to an open-shell molybdenum-based system for the first time.
• To determine the most suitable density functional for computing global and local reactivity descriptors.
• To introduce and validate new indices for assessing the quality of Koopmans' theorem approximations in DFT.

Main Methods:

• Tested 18 density functionals from the second to fourth rungs of Jacob's ladder.
• Calculated vertical ionization potentials and electron affinities.
• Defined and utilized J_I, J_A, and |ΔSL| indices to measure deviations from Koopmans' theorem.
• Applied the KID protocol to an open-shell Mo-based system.

Main Results:

• CAM-B3LYP was identified as the best-performing density functional, with M06-2X as the second-best.
• The study successfully applied the KID protocol to an open-shell system.
• New indices, J_HL and |ΔSL|, were proposed to evaluate Koopmans' theorem quality in DFT calculations.
• CAM-B3LYP and M06-2X showed the best performance in predicting reactivity descriptors for the studied system.

Conclusions:

• CAM-B3LYP is recommended as the most suitable density functional for the studied open-shell Mo-based system.
• The proposed J_HL and |ΔSL| indices offer a reliable method for selecting appropriate density functionals in DFT.
• This work extends the applicability of the KID protocol to open-shell systems, advancing reactivity descriptor calculations.