JOURNAL of the Tunisian Chemical Society

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]_n^8n- 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