Crystal structure, thermal analysis and IR spectroscopy investigations of N,N-dimethyl-1,3-propanediammonium monohydrogenmonophosphate trihydrate

A new organic monohydrogemnonophosphate (C5H16N2)HPO4.3H(2)O (abbreviate as MPAP) is prepared by reacting H3PO4 with N, N-dimethyl-1,3-propanediamine. This compound crystallizes in the orthorhombic crystal system, space group Pca2(1). Unit cell parameters are a = 8.1445(i) Angstrom, b = 11.7734(2)Angstrom, c = 12.9021(2) Angstrom, with, Z = 4 and rho(m) = 1.31 g cm(-3). The structure was solved, using the direct methods and refined against F-2 to a reliability R factor of 0.0257. Three types of hydrogen bonds participate to the structural cohesion: O(P)-(HO)-O-..., O(W)-(HO)-O-... and N-(HO)-O-.... The first one connects HPO4 groups in infinite chains. This organization of the phosphoric groups creates voids in which are located the water molecules which are themselves connected by the second type of hydrogen bonds to the adjacent phosphoric groups that lead to a typical layer organization of a polyanion [HPO4.(H2O)(3)](n)(2n-). The third hydrogen bond type is responsible for the cohesion between the two-dimensional polyanions. Thus, a framework in a three-dimensional way is then created. The thermal decomposition of MPAP shows a large endothermic effect corresponding to the elimination of the water molecules and a set of endotherms which are probably due to the evolution of ammonia from the structure and the decomposition. The title compound was also characterized by IR spectroscopy, the interpretation of the spectra is based on theoretical analyses and literature data. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.