Assessment of Density Functionals for Computing Thermodynamic Properties of Lanthanide Complexes

Area of Science:

• Organometallic Chemistry
• Computational Chemistry
• Chemical Physics

Background:

• The equilibrium between monomeric and dimeric forms of Cp*2Sm(phen) is crucial for understanding its reactivity.
• Investigating the nature of the C-C bond in the dimeric species provides insight into its stability.

Purpose of the Study:

• To elucidate the equilibrium between the radical phenanthroline complex Cp*2Sm(phen) and its coupling product (Cp*2Sm(phen))2 using computational methods.
• To determine the electronic and bonding characteristics of the C-C bond in the dimeric complex.
• To evaluate the performance of various density functionals in accurately describing the thermodynamic properties and electronic structure of the samarium complexes.

Main Methods:

• Quantum chemistry calculations were employed to study the equilibrium.
• Topological analyses were performed to characterize the C-C bond.
• A comprehensive set of density functionals was tested against experimental thermodynamic data.

Main Results:

• Topological analyses confirmed a partial covalent character of the newly formed C-C bond, explaining the observed equilibrium.
• The PBE0-D3 and M06-2X density functionals accurately reproduced experimental thermodynamic data.
• These functionals correctly described the ligand-to-metal charge transfer involving both 4f and 5d samarium orbitals.

Conclusions:

• The partial covalent nature of the C-C bond is key to the monomer-dimer equilibrium in Cp*2Sm(phen) complexes.
• PBE0-D3 and M06-2X are recommended functionals for accurate computational studies of such systems.
• Understanding these electronic transitions is vital for predicting the behavior of organometallic samarium complexes.