Professor Bess Vlaisavljevich
Professor Bess Vlaisavljevich
Department of Chemistry
University of Iowa
High-Valent f-element Coordination Complexes: Connecting Quantum Chemical Modelling to Measured Properties
The electronic structure of the coordination chemistry of the 4f-elements typically involves metal-centered valence orbitals and weak ligand fields. However, stabilizing unusually high formal oxidation states requires designing ligands that fall outside this classical paradigm. This talk explores how a combined use of density functional theory (DFT) and multiconfigurational methods can be used to understand recently synthesized high-valent praseodymium complexes. By characterizing the pseudo-tetrahedral [Pr(IV)(NPtBu3)3] complex, we examine the interplay between crystal field splitting and spin-orbit coupling. Comparisons between this complex and its isoelectronic Ce(III) analogue are attributed to differences in crystal field splitting, based on EPR measurements and theory. Moreover, this complex has an accessible Pr5+/4+ redox couple allowing it to be oxidized to form a molecular praseodymium complex in the formal +5 oxidation state, specifically [Pr(V)(NPtBu3)3]+. The complex has a multiconfigurational singlet ground state resulting from an inverted ligand field. To place the electronic structure of the 4f species in context, this talk will draw parallels to the inverted ligand fields observed in high-valent transition metal chemistry, specifically in Cu(II) species. The comparison between the 4f and 3d metals will lead into a conversation about the high- valent actinides. Specifically, the dramatic change in molecular geometry observed for a uranium(V) oxo complex. By invoking the concept of an “inverse trans influence”, we can understand the different behavior with soft-donor sulfur groups compared to the analogous oxo-donating ligands. This final section of the talk will focus on how experimental observables like structure and spectra cannot always be used alone to assign bonding but provide important metrics that, only when computed, can be used to provide the full picture of what stabilizes the structure.
Bess Vlaisavljevic
Bess Vlaisavljevich is from St. Paul, Minnesota. She received her B.A. in chemistry from the University of Minnesota Morris in 2007. She then received her M.S. and Ph.D. degrees working with Prof. Laura Gagliardi from the Department of Chemistry at the University of Minnesota Twin Cities in 2010 and 2013, respectively. Her PhD work focused on studying the electronic structure of the f-elements with multiconfigurational methods. Following this, she worked as a postdoctoral scholar at the University of California Berkeley with Prof. Berend Smit using molecular simulation and density functional theory to study gas separations and adsorption in nanoporous materials. Later, at Northwestern University with Prof. Toru Shiozaki, she was involved in developing the (X)MS-CASPT2 analytical gradient code in the program package BAGEL. In 2017, she began her independent career at the University of South Dakota. Her research focuses on using multireference quantum chemistry theories for a variety of problems in transition metal and actinide chemistry. She was recently awarded a Department of Energy Early Career Awards and USD’s Early/Mid- Career President’s research award for her efforts. In 2023, she was awarded tenure and promoted to Associate Professor. In 2024, she moved to the University of Iowa as an Associate Professor.
Hosted by Professor Anthony Schlimgen
