Ab initio multireference calculation of electronic spectra of the osmium complexes, [Os(bpy) ] and [Os(phen) ]

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Osmium complexes are vital in photochemistry and materials science.
• Accurate theoretical prediction of their spectral properties is crucial for designing new materials.
• Understanding electronic transitions, like MLCT, is key to their function.

Purpose of the Study:

• To compute and interpret the spin-orbit coupling corrected absorption spectra of osmium complexes [Os(bpy)3]2+ and [Os(phen)3]2+.
• To validate theoretical methods against experimental spectroscopic data.
• To elucidate the nature of excited states and their contribution to spectral features.

Main Methods:

• Utilized the ab initio multireference perturbation method (NEVPT2) with relativistic effects (ZORA approximation).
• Employed time-dependent Density Functional Theory (TD-DFT) for spectral calculations.
• Used all-electron basis sets for high accuracy in relativistic quantum chemical calculations.

Main Results:

• Achieved very good agreement between calculated and experimental absorption spectra.
• Accurately reproduced Metal-to-Ligand Charge Transfer (MLCT) transitions in the visible and near-UV regions.
• Provided detailed descriptions of excited states and interpreted spectra using molecular orbitals.

Conclusions:

• NEVPT2 method with relativistic corrections accurately predicts the absorption spectra of osmium complexes.
• The study enhances the understanding of electronic structures and spectral properties of osmium complexes.
• Theoretical calculations serve as a reliable tool for interpreting experimental spectra and guiding future research.