Assessment of DFT Functionals for Structural Determination of Lanthanide(III) Complexes Using Ligand Field Splitting.

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Materials Science

Background:

• Lanthanide (Ln³⁺) tetrakis complexes, denoted as C[Ln(L)₄], are crucial for various applications owing to their high quantum yields, solubility, and stability.
• The luminescent properties of these complexes are intrinsically linked to their molecular structure, especially the coordination polyhedron.
• Accurate computational methods are essential for predicting and understanding these structures.

Purpose of the Study:

• To assess the suitability of various computational methods for calculating the structures of lanthanide tetrakis complexes.
• To identify the most accurate and computationally efficient methods for modeling these systems.
• To establish a reliable approach for evaluating quantum chemical calculations based on ligand field splitting.

Main Methods:

• Density functional theory (DFT) was employed to optimize the geometries of the lanthanide complexes.
• The simple overlap model (SOM) was used to calculate ligand field (LF) energy eigenvalues.
• Root-mean-square deviation (RMSD) between experimental and calculated LF splitting (RMSD-LF) was utilized as the primary metric for method assessment.
• Various density functionals and basis sets were tested, including M06, M06-L, def2-SVP, MWB52(Eu), and CPCM.

Main Results:

• The M06 and M06-L density functionals, in conjunction with the def2-SVP/MWB52(Eu)/CPCM level of theory, provided the best accuracy-to-cost ratio.
• These selected methods demonstrated superior performance in predicting LF splitting compared to traditional RMSD-based assessments.
• The study identified specific computational parameters suitable for modeling C[Eu(L)₄] complexes.

Conclusions:

• The RMSD-LF metric offers a more precise evaluation of computational methods for lanthanide complexes than traditional structural RMSD.
• M06 and M06-L functionals are recommended for accurate and efficient modeling of C[Ln(L)₄] systems.
• This work provides a validated computational strategy for studying the structure-property relationships in luminescent lanthanide complexes.