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   Synchrotron-based methods:

X-ray absorption spectroscopy (XAS)

-EXAFS (extended X-ray absorption fine structure) for determination of metal site fine structures (metal-metal and metal-ligand distances at ~0.02 Å resolution, chemical nature and number of metal ligands).

-XANES (X-ray absorption near edge structure) for determination of metal oxidation state and site geometry. ...read more, for example here or here 

X-ray absorption linear dichroism spectroscopy (XALDS) for determination of orientations of interatomic vectors within, for example, the protein matrix, in crystals and partially oriented systems (such as proteins in biological membranes). ...read more, for example here or here

XAS under elevated gas pressure ...read more, for example here

X-ray emission spectroscopy (XES) for probing metal oxidation state, spin state, site geometry, electronic configuration, ligand structures, etc. ...read more, for example here or here

Time-resolved XAS/XES to follow structural changes and redox transitions at metal centers in time in the X-ray beam in the microseconds to hours domains. ...read more, for example here 

Resonant inelastic X-ray scattering (RIXS) to determine valence level configurations. ...read more, for example here 

Nuclear resonance vibrational spectroscopy (NRVS) to derive for example vibrational modes of metal-ligand bonds. ...read more, for example here or here

 

   Complementary spectroscopic techniques:

Element quantification by TXRF (quantification of S to Mo in proteins and model compounds with 8 orders of magnitude dynamic range)  ...read more, for example here or here

Further techniques, often used in collaborations, for example EPR for investigations on paramagnetic species, FTIR to study for example CO and CN metal ligands, photothermal spectroscopy for determination of volume and enthalpy changes in proteins (time-resolved calorimetry).

 

   Computational methods:

X-ray scattering theory using FEFF for calculation of XANES and EXAFS spectra.

Density functional theory using ORCA for obtaining geometry-optimized and energy-minimized metal site structures, spectral simulations of XAS/XES data, and electronic parameters. QM/MM approaches (Gaussian/ONIOM) for (e.g.) vibrational spectroscopy analysis. CASSCF ab-initio calculations on electronic structure of catalytic metal cofactors.