Prof. Dr. Vera Krewald
Technical University of Darmstadt, Department of Chemistry, Theoretical Chemistry Alarich-Weiss-Str. 4, 64287 Darmstadt, Germany
Exchange coupling interactions between open-shell ions in polynuclear transition metal complexes define key magnetic and spectroscopic properties of these systems. The metal coordination environment, especially the bridging ligands, determine the nature and magnitude of the magnetic coupling. This lecture will introduce phenomenological models for the interpretation of experimental data and computational chemistry methods relevant to the prediction and analysis of magnetically coupled electronic structures.
Density functional theory (DFT), in particular broken-symmetry DFT (BS-DFT), is used routinely to predict the sign, strength and origin of magnetic coupling in transition metal complexes. The advantages and intrinsic limitations of BS-DFT will be discussed.
In contrast to BS-DFT, multireference quantum-chemical calculations are in principle capable of describing each individual spin state arising from magnetic coupling of open-shell ions. The use of density matrix renormalization group (DMRG) for the description of realistic systems with multiple centers and many unpaired electrons will be outlined. In addition, a simple analytic tool that permits the identification of exchange coupling pathways in polynuclear transition metal complexes from an entanglement analysis will be introduced.
Video is available only for registered users.
(i) F. E. Mabbs, D. J. Machin. Magnetism and Transition Metal Complexes. London: Chapman & Hall, 1973.
(ii) J. P. Malrieu, R. Caballol, C. J. Calzado, C. de Graaf, N. Guihéry. ‘Magnetic Interactions in Molecules and Highly Correlated Materials: Physical Content, Analytical Derivation, and Rigorous Extraction of Magnetic Hamiltonians’. Chem. Rev. 114, 2014, 429–492. https://doi.org/10.1021/cr300500z
(iii) D. A. Pantazis, V. Krewald, M. Orio, F. Neese. ‘Theoretical Magnetochemistry of Dinuclear Manganese Complexes: Broken Symmetry Density Functional Theory Investigation on the Influence of Bridging Motifs on Structure and Magnetism’. Dalton Trans. 39, 2010, 4959–4967. https://doi.org/10.1039/c001286f
(iv) V. Krewald, F. Neese, D. A. Pantazis. ‘On the Magnetic and Spectroscopic Properties of High-Valent Mn3CaO4 Cubanes as Structural Units of Natural and Artificial Water-Oxidizing Catalysts’. J. Am. Chem. Soc. 135, 2013, 5726–5739. https://doi.org/10.1021/ja312552f
(v) M. Roemelt, V. Krewald, D. A. Pantazis. ‘Exchange Coupling Interactions from the Density Matrix Renormalization Group and N-Electron Valence Perturbation Theory: Application to a Biomimetic Mixed-Valence Manganese Complex’. J. Chem. Theory Comput. 14, 2018, 166–179. https://doi.org/10.1021/acs.jctc.7b01035
(vi) C. J. Stein, D. A. Pantazis, V. Krewald. ‘Orbital Entanglement Analysis of Exchange-Coupled Systems’. J. Phys. Chem. Lett. 10, 2019, 6762–6770. https://doi.org/10.1021/acs.jpclett.9b02417