title: 1,2-dimethyl-4-nitro-5-morpholinoimidazole and its hydrate: a case of a centrosymmetric-noncentrosymmetric ambiguity.
abstract: The compound studied is 1,2-dimethyl-4-nitro-5-morpholinoimidazole (1) in its anhydrous (1) and hydrated [(1).H(2)O] crystal forms. In spite of the strong electron-withdrawing effect of the nitro group, the unsubstituted N atom of the imidazole moiety retains its basic character and acts as an acceptor for intermolecular hydrogen bonds: either weak C-H....N bonds in (1) or strong O-H...N bonds, with the water molecules, in (1).H(2)O. The packing in (1) is determined by weak C-H.N and C-H.O hydrogen bonds, van der Waals interactions and the stacking of imidazole fragments. The crystal structure of (1).H(2)O is determined by strong O-H(water)...N3(imidazole) and O-H(water)...O(water) hydrogen bonds. This structure consists of a centrosymmetric 'matrix' of imidazole derivative molecules and locally noncentrosymmetric arrays of hydrogen-bonded water molecules. Each of these arrays is strictly homodromic, i.e. it runs only in one direction:.H-O....H-O....H-O.... or....O-H....O-H....O-H.... These homodromic domains are statistically distributed within the crystal.
authors.affiliation: Department of Crystallography, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Kubicki
authors.forename: Teresa
authors.initials: T
authors.lastname: Borowiak
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Dutkiewicz
authors.forename: Stanisław
authors.initials: S
authors.lastname: Sobiak
authors.forename: Iwona
authors.initials: I
authors.lastname: Weidlich