Etudes spectrometrique IR, calorimetrique et RMN de 1H, 31P, 7Li du cyclotetraphosphate: NaLi[NH 3-(CH 2) 2-NH 3]P 4O 12 · 3H 2O
Abstract
According to the previous single-crystal X-ray structure determination the cyclotetraphosphate NaLi[NH 3-(CH 2) 2-NH 3]P 4O 12 · 3H 2O belongs to the Pcca ( D82 h) space group (M. Bdiri and A. Jouini, J. Solid State Chem. 83, 350 (1989)); there are four anions per unit cell at a C2 symmetry site. A vibrational spectroscopy is expected to give real information about the geometry of the P 4O 12 group since its symmetry determines the number of normal vibration modes and their IR and Raman activities. According to the IR spectrum and a theoretical group analysis, symmetry of the ring anion P 4O 4-12 is found to be idealized from C2 to C2 v symmetry site. An assignment of observed bands at room temperature is proposed. Thermodynamic parameters of dehydration, ΔH and Ea, are determined by differential scanning calorimetry (DSC). Experimental NMR absorption lineshapes, for 1H, 31P, and 7Li nuclei in the solid state, at temperatures between 170 and 300 K, have been carefully examined. Analysis of 1H data indicates the rigid character of CH 2 groups and the reorientation motion of proton in H 2O and NH 3. Analysis of static and MAS absorption lineshapes for the 31 P ( I = 1/2) and 7Li ( I = 3/2) resonance in the title compound leads to two tetrahedral atomic sites for phosphorous and to one for lithium, in agreement with the X-ray crystallographic studies. The 7 Li NMR spectrum obtained at low temperature suggests a static distribution so that only half of the Li general positions is occupied.
- Publication:
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Journal of Solid State Chemistry France
- Pub Date:
- January 1994
- DOI:
- 10.1006/jssc.1994.1020
- Bibcode:
- 1994JSSCh.108..134B