Chemical preparation and crystal structure are given for a new cyclotetraphosphate: [3,5-(CH3)(2)C6H3NH3](4)P4O12.3H(2)O. This compound is triclinic P1 with the following unit-cell parameters: a = 8.298(3), b = 8.299(3), c = 17.242(7)Angstrom, alpha = 97.13(3), beta = 102.72(3), gamma = 64.55(3)degrees, Z = 1 and V = 1045.2(8)Angstrom(3). The crystal structure has been solved and refined to R = 0.040 using 6086 independent reflections. The atomic arrangement can be described as layers organization. Layers built by P4O12 ring anions, ammonium groups and water molecules parallel to the plan (001), between which the organic groups are located. Characterization by X-ray diffraction, IR absorption, and thermal analysis are described. (C) 2003 Elsevier Ltd. All rights reserved.