TY - JOUR
T1 - Low temperature structural transformation in T[Ni(CN)4]·xpyz with x=1,2; T=Mn,Co,Ni,Zn,Cd; pyz=pyrazine
AU - Rodríguez-Hernández, J.
AU - Lemus-Santana, A. A.
AU - Ortiz-López, J.
AU - Jiménez-Sandoval, S.
AU - Reguera, E.
N1 - Funding Information:
A.A.L.-S acknowledges the support provided by CONACyT (Mexico) and UNAM Environmental Nanotechnology Project (PUNTA) for her PhD studies. The help of M. Avila-Santos for HR-XRD data collection and of F. Rodríguez-Melgarejo for the Raman spectra acquisition is highly appreciated. This research was partially supported by the Projects SEP-CONACyT-2007-61-541 and ICyTDF-PIFUTP08-158. Access to the LNLS synchrotron radiation facility (at Campinas, Brazil) is also acknowledged.
PY - 2010/1
Y1 - 2010/1
N2 - The materials under study are pillared solids T[Ni(CN)4]·xpyz with one and two (x=1,2) pyrazine (pyz) molecules and where T=Mn, Co, Ni, Zn, Cd. Stimulated by their structural features and potential role as prototype of porous solids for hydrogen storage, the structural stability under cryogenic conditions for this series of pillared solids was studied. At low temperature, in the 100-200 K range, the occurrence of a reversible structural transformation was found. For T=Mn, Co, Zn, Cd, with x=2, the structural transformation was observed to occur around 185 K, and the low temperature phase crystallizes with a monoclinic unit cell (space group Pc). This structure change results from certain charge redistribution on cooling within the involved ligands. For T=Ni with x=1, both the low and high temperature phases crystallize with unit cells of tetragonal symmetry, within the same space group but with a different unit cell volume. In this case the structure change is observed around 120 K. Above that temperature the rotational states for the pyrazine molecule are thermally excited and all the pyrazine molecules in the structure become equivalent. Under this condition the material structure is described using a smaller structural unit. The structural study using X-ray powder diffraction data was complemented with calorimetric and Raman spectroscopy measurements. For the low temperature phases the crystal structures were solved from Patterson methods and then refined using the Rietveld method.
AB - The materials under study are pillared solids T[Ni(CN)4]·xpyz with one and two (x=1,2) pyrazine (pyz) molecules and where T=Mn, Co, Ni, Zn, Cd. Stimulated by their structural features and potential role as prototype of porous solids for hydrogen storage, the structural stability under cryogenic conditions for this series of pillared solids was studied. At low temperature, in the 100-200 K range, the occurrence of a reversible structural transformation was found. For T=Mn, Co, Zn, Cd, with x=2, the structural transformation was observed to occur around 185 K, and the low temperature phase crystallizes with a monoclinic unit cell (space group Pc). This structure change results from certain charge redistribution on cooling within the involved ligands. For T=Ni with x=1, both the low and high temperature phases crystallize with unit cells of tetragonal symmetry, within the same space group but with a different unit cell volume. In this case the structure change is observed around 120 K. Above that temperature the rotational states for the pyrazine molecule are thermally excited and all the pyrazine molecules in the structure become equivalent. Under this condition the material structure is described using a smaller structural unit. The structural study using X-ray powder diffraction data was complemented with calorimetric and Raman spectroscopy measurements. For the low temperature phases the crystal structures were solved from Patterson methods and then refined using the Rietveld method.
KW - Crystal chemistry
KW - Layered compounds
KW - Low temperature structure
KW - Pillared solids
UR - http://www.scopus.com/inward/record.url?scp=73349107750&partnerID=8YFLogxK
U2 - 10.1016/j.jssc.2009.11.004
DO - 10.1016/j.jssc.2009.11.004
M3 - Artículo
SN - 0022-4596
VL - 183
SP - 105
EP - 113
JO - Journal of Solid State Chemistry
JF - Journal of Solid State Chemistry
IS - 1
ER -