JOURNAL of the Tunisian Chemical Society

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Characterization of a new organic-cation cyclotetraphosphate: [NH3(CH2)4 NH3]2 P4O12. 9/2H20

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Chemical preparation, differential scanning calorimetric analysis, IR spectrometric investigation and crystal structure are given for a new organic condensed phosphate. The putrescinium cyclotetraphosphate hydrate [NH3(CH2)4NH3)2P4O12.9/2H2O is monoclinic C2/c with Z=8 and unit cell dimensions: a=38.87(2)Å, b=9.478(2)Å, c=13.97(2)Å, β=96.51(7)°. The structure was refined to a final Rw value of 0.031. The atomic arrangement is a typical layer organization built by alternating layers of anions and cations. The anion layers, including P4O12 rings and water molecules, are in planes centered on z=1/4 and 3/4, while the cation layers, made up by the three independent putrescinium dications [NH3(CH2)4NH3]2+, are in planes centered on z=0.0 and 1/2. All the N–H...O hydrogen bonds are established between adjacent layers while the O–H...O bonds operate within the anionic layer linking (i) two P4O12 groups to form clusters: [(P4O12)2(H2O)3]8-, (ii) clusters to form infinite ribbons: [(P4O12)2(H2O)7]n8n- and (iii) ribbons to form an infinite two-dimensional layer. The DSC study shows that the dehydration occurs in three steps. Such dehydration process may be related to the different environments of the water molecules in H-bond schemes. The reported IR investigation, indicates a satisfactory agreement between the predicted, on the basis of a group theoretical analysis, and the observed P4O12 stretching bands, especially in the 800-600 cm-1 characteristic region for C1 symmetry.

H. Thabet, M. Bdiri, A. Jouini, A. Durif

Pages 693-708

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