On the microporous nature of transition metal nitroprussides
Por:
Balmaseda J., Reguera E., Gomez A., Roque J., Vazquez C., Autie M.
Publicada:
1 ene 2003
Resumen:
Nitroprussides of divalent transition metals form a family of microporous molecular materials. Their properties in this sense depend on the transition metal cation involved and also on the preparative method, which determine their crystal structures. The stable phases of this family of materials belong to one of the following crystal structures: orthorhombic (Pnma) (Mn2+, Fe2+, Cu2+, Zn2+, and Cd2+), cubic (Fm3m) (Co2+ and Ni2+), and orthorhombic (Amm2) (Cu2+). These materials are stable up to above 160°C, while their dehydration takes place around 100°C. On dehydration, Amm2 copper complex changes into a tetragonal (I4mm) phase. The microporous nature of these materials is discussed according to their crystal structure and correlating structural and adsorption data. The accessibility to the pore system was evaluated through adsorption of H2O, CO2, and N2. Pores of both orthorhombic and cubic structures are accessible to H2O and CO2 in experiments carried out at 23 and 0°C, respectively; however, they are inaccessible to N2 at -196°C. This behavior is discussed as related to the large polarizing power of the nitrosyl (NO) ligand which distorts the local environment of the iron atom and reduces the effective window cross section. The small pores of tetragonal copper nitroprusside were inaccessible to the adsorbates used.
Filiaciones:
Balmaseda J.:
Institute of Materials and Reagants, University of Havana, San Lazaro and L, 10400 Havana, Cuba
Reguera E.:
Institute of Materials and Reagants, University of Havana, San Lazaro and L, 10400 Havana, Cuba
Gomez A.:
Institute of Materials and Reagants, University of Havana, San Lazaro and L, 10400 Havana, Cuba
Roque J.:
Institute of Materials and Reagants, University of Havana, San Lazaro and L, 10400 Havana, Cuba
Vazquez C.:
Institute of Materials Research, UNAM, Mexico, Mexico
Autie M.:
National Center for Scientific Res., Havana, Cuba
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