Comparative studies of quasi‐relativistic density functional methods for the description of lanthanide and actinide complexes

Abstract

We present a comparative Density Functional Theory (DFT) study based on two different implementations of relativistic effects within the Kohn-Sham (KS) approach, to describe the metal-ligand interaction in I(3)M-L complexes (L = NH(3), NCCH(3), CO and M = La, Nd, U). In the first model, the scalar corrections were included by a quasi-relativistic approach (QR) via the so-called ZORA or Pauli Hamiltonians, while in the second, these effects are taken into account in a quasi-Relativistic Effective Core Potential (RECP). These relativistic approaches were used in conjunction with various gradient corrected (GGA) or hybrid (SCH) functionals. The structural parameters obtained from geometry optimizations have been compared to experimental structural trends, and rationalized by a KS orbital analysis. Both approaches provide similar results for mainly ionic metal-ligand bonds (e.g., for the sigma-donor ligand L = NH(3)). For the pi-acceptor ligands (NCCH(3), CO), the QR approach is in agreement with experimental trends and consistent with the presence of a backbonding interaction between U(III) and the neutral ligand, which does not exist in the lanthanide homologues. The GGA/RECP methods also reproduce this phenomenon, while the SCH/RECP scheme fails to describe this interaction. The role of the RECP, of its size, and of additional polarization functions has also been examined. Finally, the failure of the SCH/RECP approach was interpreted as a consequence of a bad estimation of frontier orbital energy levels in the uranium and ligand species.

A Macrocyclic Chelator That Selectively Binds Ln4+ over Ln3+ by a Factor of 1029

“…It is important to note that the energetic stabilization gained due to 4f covalency is proportional to the overlap between 4f and ligand-based orbitals. 173,175 Hence, because the radial extension of the 4f orbitals is very small, [176][177][178][179] increasing 4f covalency by decreasing the energy separation of the metal and ligand orbitals may act to weaken the bond overall by decreasing the amount of ionic character in the ground state. This work also illustrates that thermodynamic, spectroscopic, and theoretical studies of tetravalent cerium molecules is a fruitful area for research.…”

DFT modeling of the relative affinity of nitrogen ligands for trivalent f elements: an energetic point of view

“…[43][44][45] The theoretical treatment of trivalent f elements complexes with ADF has been several times investigated. 29,33,46,47 Density Functional Theory was found to be an effective tool for the description of ground states of the f-elements when applied with the scalar relativistic ZORA approach and the Becke-Perdew GGA functional. 48 In recent papers, the DFT approach was also found to properly reproduce experimental thermodynamic trends, whereas post Hartree-Fock methods (CASPT2, MP2) were required to reach a better quantitative agreement.…”

A Theoretical Study of the Structure and Bonding of UOX4(X=F, Cl, Br, I) Molecules: The Importance of InverseTransInfluence

“…As these methods are often used in actinide research, [7,10,[33][34][35] we found it important to devote a discussion to the results. 1 The performance of the three theoretical levels will be compared jointly with the discussion of the characteristic structures in Section 2.1.…”