Post-B3LYP Functionals Do Not Improve the Description of Magnetic Coupling in Cu(II) Dinuclear Complexes

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Magnetochemistry

Background:

• Accurate prediction of magnetic coupling constants is crucial for understanding molecular magnetism.
• Existing computational methods, particularly density functional theory (DFT) functionals, show varying performance for open-shell systems.

Purpose of the Study:

• To evaluate the accuracy of post-B3LYP exchange-correlation functionals for predicting magnetic coupling constants in Cu(II) dinuclear complexes.
• To establish a reliable open-shell database for training and reparametrizing DFT functionals.

Main Methods:

• Analysis of post-B3LYP functionals using an open-shell database of Cu(II) dinuclear complexes.
• Assessment of hybrid and range-corrected hybrid functionals against experimental magnetic coupling constants.
• Identification of reliable functionals based on accuracy for different magnetic interaction strengths.

Main Results:

• Hybrid functionals with 25-40% Fock exchange, such as SOGGA and PBE0, show good accuracy for moderate-to-strong antiferromagnetic interactions.
• Range-corrected hybrids like CAM-B3LYP and ωB97XD offer acceptable results, while M11 is more erratic.
• Accuracy is system- and range-dependent, with a notable difference in performance for ferromagnetic versus antiferromagnetic interactions.

Conclusions:

• Blindly applying a single functional for magnetic coupling constant prediction is unreliable.
• Standardizing computational methods and selecting optimal functionals are essential for extracting meaningful magnetostructural correlations.
• The developed database serves as a valuable resource for improving DFT functional fitting schemes.