Crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitro-acetonitrile (C7H11N5O2) and 2,6-dianlino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]-pyrimidin-7-one monohydrate (C6H6N6O4 center dot H2O) fromX-ray, synchrotron and neutron powder diffraction data

The crystal and molecular structures of 2-[1-(2-aminoethyl) -2-imidazolidin ylidene]-2-nitroacetonitrile [C7H11N5O2; space group P2(1)/n; Z = 4; a = 7. 4889 (8), b = 17.273 (2), c = 7.4073 (8) Angstrom, beta = 111.937 (6)degree s], (I), and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo [1,5-a]-pyrimidin-7- one monohydrate [C6H6N6O4. H2O; space group P2(1)/n; Z = 4; a 17.576(3), b = 10.900(2), 4.6738 (6) Angstrom, beta = 9..867(8)degrees], (II), have been determined from X-ray, synchrotron and neutron powder diffraction data usi ng various methods. The structures were originally solved from Guinier phot ographs with a grid search procedure and the program MRIA using a priori in formation from NMR and mass spectra on the possible geometry of the molecul es. Because the conformation of molecule (I) changed during the bond-restra ined Rietveld refinement, solvent water was found in (II) and, moreover, as both Guinier patterns were corrupted by texture, high-resolution texture-f ree synchrotron data were collected at the BM16 beamline, ESRF to confirm t he original results. Using the set of \F\(2) values derived from the synchr otron patterns after full-pattern decomposition procedures, the structures of (I) and (II) were solved by direct methods via SHELXS96, SIRPOW.92 and P OWSIM without any preliminary models of the molecules, and by Patterson sea rch methods via DIRDIF96 and PATSEE with the use of rigid fragments from ea ch of the molecules. The neutron patterns allowed (I) and (II) to be solved using the grid search procedure and correct initial models of the molecule s including H atoms. The results obtained from powder patterns measured on different devices demonstrate the high level of reproducibility and reliabi lity of various powder software and equipment, with a certain preference fo r synchrotron facilities.