Low temperature structural transformation in T[Ni(CN){sub 4}].xpyz with x=1,2; T=Mn,Co,Ni,Zn,Cd; pyz=pyrazine

Journal Article · Fri Jan 15 00:00:00 EST 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.11.004· OSTI ID:21372455

Rodriguez-Hernandez, J ^[1]; Lemus-Santana, A A ^[2]; Ortiz-Lopez, J ^[3]; Jimenez-Sandoval, S ^[4]; Reguera, E ^[5]

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1. Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada del IPN, Unidad Legaria, Mexico, D.F. Mexico (Mexico)
2. Departamento de Polimeros, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico, D.F. Mexico (Mexico)
3. Escuela Superior de Fisica y Matematicas del IPN, UP 'ALM', Col. Lindavista, Mexico, D.F. (Mexico)
4. Centro de Investigacion y Estudios Avanzados del IPN, Unidad Queretaro, Queretaro (Mexico)
5. Instituto de Ciencia y Tecnologia de Materiales, Universidad de La Habana (Cuba)

The materials under study are pillared solids T[Ni(CN){sub 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. - Graphical abstract: Low temperature ordered structure for pyrazine in T[Ni(CN){sub 4}].pyz.

• OSTI ID: 21372455
• Journal Information: Journal of Solid State Chemistry, Vol. 183, Issue 1; Other Information: DOI: 10.1016/j.jssc.2009.11.004; PII: S0022-4596(09)00516-7; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CADMIUM COMPLEXES
CALORIMETRY
COBALT COMPLEXES
CYANIDES
HYDROGEN STORAGE
MANGANESE COMPLEXES
MONOCLINIC LATTICES
PATTERSON METHOD
POROUS MATERIALS
RAMAN SPECTROSCOPY
ROTATIONAL STATES
SPACE GROUPS
TEMPERATURE RANGE 0065-0273 K
X-RAY DIFFRACTION
ZINC COMPLEXES
CALCULATION METHODS
COHERENT SCATTERING
COMPLEXES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
ENERGY LEVELS
EXCITED STATES
LASER SPECTROSCOPY
MATERIALS
SCATTERING
SPECTROSCOPY
STORAGE
SYMMETRY GROUPS
TEMPERATURE RANGE
TRANSITION ELEMENT COMPLEXES