TD-DFT Benchmark on Inorganic Pt(II) and Ir(III) Complexes

Area of Science:

• Computational Chemistry
• Inorganic Chemistry
• Quantum Chemistry

Background:

• Accurate prediction of electronic excitation energies is crucial for understanding and designing metal complexes.
• Density Functional Theory (DFT) is a powerful tool for computational chemistry, but the choice of functional and basis set can significantly impact results.

Purpose of the Study:

• To comprehensively investigate and compare the performance of various Density Functional Theory (DFT) functionals and basis sets for calculating one-photon absorption spectra of platinum (Pt) and iridium (Ir) complexes.
• To identify reliable computational methods for predicting the optical properties of these transition metal complexes.

Main Methods:

• Employed time-dependent density functional theory (TD-DFT) calculations.
• Investigated 4 iridium and 7 platinum complexes.
• Compared nine different DFT functionals (GGA, global hybrids, range-separated hybrids) and two basis sets (LANL2DZ, def2-TZVP with pseudopotentials).

Main Results:

• Hybrid functionals (e.g., B3LYP, PBE0) provide comparable and accurate excitation energies, irrespective of the correlation functional.
• More recent functionals (CAM-B3LYP, M06-2X) tend to overestimate energies, while local functionals (BP86, M06-L) underestimate them.
• Basis set effects are minimal, with triple-ζ basis sets offering no significant improvement over double-ζ plus polarization but increasing computational cost.

Conclusions:

• Hybrid DFT functionals are recommended for accurate calculations of one-photon absorption spectra in Pt(II) and Ir(III) complexes.
• Computational efficiency should be considered when selecting basis sets, as simpler sets can yield adequate results.