TY - JOUR
T1 - Nature of the observed asymmetry in mossbauer spectra of iron (2+) hexacyanometallates (III)
AU - Reguera, E.
AU - Yee-Madeira, H.
AU - Demeshko, S.
AU - Eckold, G.
AU - Jimenez-Gallegos, J.
N1 - Funding Information:
This study was partially supported by the project SEP-CONACyT 2007–61541. The authors thank C. N. Vargas for the material preparation. The access to the LNLS synchrotron radiation facility to obtain XRD powder patterns under vacuum and at different temperatures is also acknowledged.
PY - 2009
Y1 - 2009
N2 - The material under study belongs to the Prussian blue analogues family, which are coordination compounds with a porous framework appropriate for the storage of small molecules, among them hydrogen. The porous framework results from systematic vacancies for the octahedral building block, [M(CN) 6], in a 3D structure. Mössbauer spectroscopy is a powerful tool to obtain structural information on the local environment for the iron nucleus in these materials. Mössbauer spectra of iron (2+) hexacyanometallates (III) show two slightly asymmetric quadrupole splitting doublets. These two doublets correspond to two non-equivalent structural sites for the iron atom in the framework related with a non-random vacancy distribution. The observed asymmetry was ascribed to a vibrational anisotropy for these iron sites. The asymmetry decreases on the sample cooling and for 7 K it practically disappears. The iron atom is found at the cavities surface with a mixed coordination sphere, Fe(NC)6-r(H2O)r. Such anisotropic coordination environment could explain the presence of certain vibrational anisotropy detected as asymmetric quadrupole splitting doublets.
AB - The material under study belongs to the Prussian blue analogues family, which are coordination compounds with a porous framework appropriate for the storage of small molecules, among them hydrogen. The porous framework results from systematic vacancies for the octahedral building block, [M(CN) 6], in a 3D structure. Mössbauer spectroscopy is a powerful tool to obtain structural information on the local environment for the iron nucleus in these materials. Mössbauer spectra of iron (2+) hexacyanometallates (III) show two slightly asymmetric quadrupole splitting doublets. These two doublets correspond to two non-equivalent structural sites for the iron atom in the framework related with a non-random vacancy distribution. The observed asymmetry was ascribed to a vibrational anisotropy for these iron sites. The asymmetry decreases on the sample cooling and for 7 K it practically disappears. The iron atom is found at the cavities surface with a mixed coordination sphere, Fe(NC)6-r(H2O)r. Such anisotropic coordination environment could explain the presence of certain vibrational anisotropy detected as asymmetric quadrupole splitting doublets.
KW - Crystal structure
KW - Mossbauer spectra
KW - Porous solids
KW - Prussian blue analogues
UR - http://www.scopus.com/inward/record.url?scp=68149148843&partnerID=8YFLogxK
U2 - 10.1524/zpch.2009.5455
DO - 10.1524/zpch.2009.5455
M3 - Artículo
SN - 0942-9352
VL - 223
SP - 701
EP - 711
JO - Zeitschrift fur Physikalische Chemie
JF - Zeitschrift fur Physikalische Chemie
IS - 6
ER -