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Multireference Electronic Structures of Fe-Pyridine(diimine) Complexes over Multiple Oxidation States
Manuel A Ortuño1, Christopher J Cramer1
1Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455, United States.
The Journal of Physical Chemistry. A
|July 14, 2017
Summary
Redox-active ligands, like pyridine(diimine) compounds, present complex electronic structures. Advanced RASSCF/RASPT2 calculations accurately describe iron complexes, revealing their multiconfigurational nature and electronic ground states.
Area of Science:
- Coordination Chemistry
- Computational Chemistry
- Materials Science
Background:
- Noninnocent (redox-active) ligands, particularly pyridine(diimine) (bis(imino)pyridine) derivatives, are crucial for developing earth-abundant transition metal catalysts.
- The intricate electronic structures of these metal complexes often challenge standard computational methods like Kohn-Sham density functional theory (DFT).
- Accurate characterization of geometries, charge distributions, and spin-state energetics is vital for understanding their reactivity and catalytic potential.
Purpose of the Study:
- To investigate the electronic structure of iron pyridine(diimine) complexes across three oxidation states.
- To demonstrate the utility of multi-reference computational methods for accurately describing these complex systems.
- To provide insights into the electronic ground states and charge distributions of these important catalytic compounds.
Main Methods:
- Utilized Restricted Active Space Self-Consistent Field (RASSCF) and Restricted Active Space Perturbation Theory (RASPT2) calculations.
- Applied these advanced quantum chemical methods to model iron pyridine(diimine) complexes.
- Focused on analyzing geometries, charge distributions, and spin-state properties.
Main Results:
- The calculations revealed the highly multiconfigurational electronic character inherent to these iron pyridine(diimine) complexes.
- RASSCF/RASPT2 methods provided quantitatively accurate descriptions of geometries and charge distributions.
- Insights into the electronic ground states and spin-state energy separations were obtained, highlighting the limitations of single-reference methods.
Conclusions:
- Advanced multi-reference methods like RASSCF/RASPT2 are essential for accurately describing the electronic properties of redox-active ligand complexes.
- These computational approaches offer valuable insights into the fundamental electronic structure governing the reactivity of earth-abundant metal catalysts.
- The study underscores the complexity of noninnocent ligand systems and the need for sophisticated theoretical tools.
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