Abstract
Lanthanides (Ln) are typically found in the +3 oxidation state. However, in recent decades, their chemistry has been expanded to include the less stable +2 oxidation state across the entire series except promethium (Pm), facilitated by the coordination of ligands such as trimethylsilylcyclopentadienyl, C5H4SiMe3 (Cp0). The ½LnCp03]- complexes have been the workhorse for the synthesis and theoretical study of the fundamental aspects of divalent lanthanide chemistry, where experimental and computational evidence have suggested the existence of different ground state (GS) configurations, 4fn+1 or 4fn5d1, depending on the specific metal. Standard reduction potentials and 4fn+1 to 4fn5d1 promotion energies have been two factors usually considered to rationalize the occurrence of these variable GS configurations, however the driving force behind this phenomenon is still not clear. In this work we present a comprehensive theoretical approach to shed light on this matter using the [LnCp3]− model systems. We begin by calculating 4fn+1 to 4fn5d1 promotion energies and successfully correlate them with existing experimental data. Furthermore, we analyze how changes in the GS charge distribution between the Ln ions, LnCp3 and the reduced [LnCp3]− complexes (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) correlate with experimental trends in redox potentials and the calculated promotion energies. For this purpose, a comprehensive theoretical work that includes relativistic ligand field density functional theory (LFDFT) and relativistic ab initio wavefunction methods was performed. This study will help the rational design of suitable environments to tune the different GS configurations as well as modulating the spectroscopic properties of new Ln2+ complexes.
| Original language | English |
|---|---|
| Pages (from-to) | 2024-2033 |
| Number of pages | 10 |
| Journal | Chemical Science |
| Volume | 16 |
| Issue number | 4 |
| DOIs | |
| State | Published - Jan 3 2025 |
Funding
This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Geo-sciences, Biosciences and Heavy Elements Chemistry Program, under award number DE-SC0023693 (T. E. A.) and the U.S. National Science Foundation under award CHE-2154255 (W. J. E). M. J. B.-L. acknowledge the postdoctoral support provided by the Glenn T. Seaborg Institute. The authors thank Professor Zoila Barandiaran for her valuable input on the theoretical treatment of these systems and Valentina Villegas for her help designing the TOC. This work was partially executed at Los Alamos National Laboratory. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of the U.S. Department of Energy (contract no. 89233218CNA000001). This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, Biosciences and Heavy Elements Chemistry Program, under award number DE-SC0023693 (T. E. A.) and the U.S. National Science Foundation under award CHE-2154255 (W. J. E). M. J. B.-L. acknowledge the postdoctoral support provided by the Glenn T. Seaborg Institute. The authors thank Professor Zoila Barandiaran for her valuable input on the theoretical treatment of these systems and Valentina Villegas for her help designing the TOC. This work was partially executed at Los Alamos National Laboratory. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of the U.S. Department of Energy (contract no. 89233218CNA000001).