Crystal structure, vibrational spectra, and thermal decomposition and nitrogen adsorption behaviour of a new tetramanganese(II) dipyrophosphate decahydrate, Mn4(P2O7)2·10H2O

Autor: Janusz A. Kozinski, Ian S. Butler, Hassane Assaaoudi
Rok vydání: 2006
Předmět:
Zdroj: Journal of Chemical Crystallography. 36:723-733
ISSN: 1572-8854
1074-1542
DOI: 10.1007/s10870-006-9127-z
Popis: A new manganese(II) pyrophosphate, Mn4(P2O7)2·10H2O, has been synthesized and characterized by single-crystal X-ray diffraction [orthorhombic space group Pnma, with unit cell parameters of a=9.3288(3) A, b=25.9532(9) A, c=8.4783(3) A; Z=4]. All the pyrophosphate anions show non-linear P–O–P bonds with an average angle of 128.60°. The framework of this new pyrophosphate is made up of packed layers of MnO6 octahedra connected by double-tetrahedra P2O7 groups and a layer of Mn(H2O)6 units. The [P2O7]4− anions adopt a bent, near-staggered conformation. The absence of coincidences for the majority of the IR and Raman bands is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted in part on the basis of factor group effects. The structural changes occurring during heating have been investigated by TG-ATD. When Mn4(P2O7)2 .10H2O is gradually heated, it decomposes into an intermediate hydrated salt at 96°C and then to anhydrous Mn2P2O7 at 325°C. This thermal behaviour is different from that of Zn4(P2O7)2·10H2O. The crystal structure of the new managenese(II) pyrophosphate is compared with the known structures of Zn4(P2O7)2·10H2O, Mn2P2O7·2H2O and anhydrous Mn2P2O7. The adsorption and desorption isotherms of Mn4(P2O7)2·10H2O, Zn4(P2O7)2·10H2O and MnKHP2O7·2H2O have been investigated by BET measurements and the results show that the capacity for N2 sorption of the Mn(II) salt is two times lower than is that of the Zn(II) isotype and two or three times higher than is that of MnKHP2O7·2H2O.
Databáze: OpenAIRE
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