An experimental XAS and ab initio approach to describe the electronic and local structure of sodium nitroprussiate single crystals

Abstract The electronic and local structural properties of single crystals in the ground state (GS) of the photo-switchable compound Na2[Fe(CN)5NO]•2H2O (sodium nitroprussiate, SNP) have been investigated by X-ray Absorption Fine Structure Spectroscopy (XAFS) and FEFF simulations. In SNP, the XANES (X-ray Absorption Near Edge Structure) pre-edge region presents three distinct peaks with different intensities depending on the crystal axis orientation with respect to the polarization direction of the X-ray beam. The peaks correspond to a combination of 1s to 4p and 1s to 3d transitions with possibly mixed dipole and quadrupole character. The EXAFS fitting reveals, as expected, a biased structure according to the relative position of the crystal with respect to the beam polarization and the fittings are in accordance to theoretical values. The best fitted model has a large contribution from multi-scattering paths, which clarifies the interpretation of the actual peak contributions on the Fourier Transformed signal.