TY  - GEN
A1  - Kubin, Markus
A1  - Guo, Meiyuan
A1  - Kroll, Thomas
A1  - Löchel, Heike
A1  - Källman, Erik
A1  - Baker, Michael L.
A1  - Mitzner, Rolf
A1  - Gul, Sheraz
A1  - Kern, Jan
A1  - Föhlisch, Alexander
A1  - Erko, Alexei
A1  - Bergmann, Uwe
A1  - Yachandra, Vittal
A1  - Yano, Junko
A1  - Lundberg, Marcus
A1  - Wernet, Philippe
T1  - Probing the oxidation state of transition metal complexes
BT  - a case study on how charge and spin densities determine Mn L-edge X-ray absorption energies
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Transition metals in inorganic systems and metalloproteins can occur in different oxidation states, which makes them ideal redox-active catalysts. To gain a mechanistic understanding of the catalytic reactions, knowledge of the oxidation state of the active metals, ideally in operando, is therefore critical. L-edge X-ray absorption spectroscopy (XAS) is a powerful technique that is frequently used to infer the oxidation state via a distinct blue shift of L-edge absorption energies with increasing oxidation state. A unified description accounting for quantum-chemical notions whereupon oxidation does not occur locally on the metal but on the whole molecule and the basic understanding that L-edge XAS probes the electronic structure locally at the metal has been missing to date. Here we quantify how charge and spin densities change at the metal and throughout the molecule for both redox and core-excitation processes. We explain the origin of the L-edge XAS shift between the high-spin complexes Mn-II(acac)(2) and Mn-III(acac)(3) as representative model systems and use ab initio theory to uncouple effects of oxidation-state changes from geometric effects. The shift reflects an increased electron affinity of Mn-III in the core-excited states compared to the ground state due to a contraction of the Mn 3d shell upon core-excitation with accompanied changes in the classical Coulomb interactions. This new picture quantifies how the metal-centered core hole probes changes in formal oxidation state and encloses and substantiates earlier explanations. The approach is broadly applicable to mechanistic studies of redox-catalytic reactions in molecular systems where charge and spin localization/delocalization determine reaction pathways.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 656 
KW  - electronic-structure
KW  - atomic multiplet
KW  - water-oxidation
KW  - iron complexes
KW  - photosystem-II
KW  - spectroscopy
KW  - manganese
KW  - spectra
KW  - ligand
KW  - FE
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-425057
SN  - 1866-8372
IS  - 656
ER  - 
TY  - GEN
A1  - Norell, Jesper
A1  - Jay, Raphael Martin
A1  - Hantschmann, Markus
A1  - Eckert, Sebastian
A1  - Guo, Meiyuan
A1  - Gaffney, Kelly J.
A1  - Wernet, Philippe
A1  - Lundberg, Marcus
A1  - Föhlisch, Alexander
A1  - Odelius, Michael
T1  - Fingerprints of electronic, spin and structural dynamics from resonant inelastic soft X-ray scattering in transient photo-chemical species
T2  - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe
N2  - We describe how inversion symmetry separation of electronic state manifolds in resonant inelastic soft X-ray scattering (RIXS) can be applied to probe excited-state dynamics with compelling selectivity. In a case study of Fe L-3-edge RIXS in the ferricyanide complex Fe(CN)(6)(3-), we demonstrate with multi-configurational restricted active space spectrum simulations how the information content of RIXS spectral fingerprints can be used to unambiguously separate species of different electronic configurations, spin multiplicities, and structures, with possible involvement in the decay dynamics of photo-excited ligand-to-metal charge-transfer. Specifically, we propose that this could be applied to confirm or reject the presence of a hitherto elusive transient Quartet species. Thus, RIXS offers a particular possibility to settle a recent controversy regarding the decay pathway, and we expect the technique to be similarly applicable in other model systems of photo-induced dynamics.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 779 
KW  - charge-transfer
KW  - relaxation dynamics
KW  - absorption-spectra
KW  - energy-conversion
KW  - basis-sets
KW  - ab-initio
KW  - complexes
KW  - photoelectron
KW  - spectroscopy
KW  - simulations
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-437493
SN  - 1866-8372
IS  - 779
SP  - 7243
EP  - 7253
ER  -