1,2-Dimethyl-4-nitro-5-morpholinoimidazole and its hydrate: a case of a centrosymmetric-noncentrosymmetric ambiguity

• Published in: Acta crystallographica. Section B, Structural science Vol. 59; no. 4; pp. 487 - 491
• Main Authors: Kubicki, Maciej, Borowiak, Teresa, Dutkiewicz, Grzegorz, Sobiak, Stanisław, Weidlich, Iwona
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.08.2003; Blackwell
• Subjects: Condensed matter: structure, mechanical and thermal properties; disorder; Exact sciences and technology; Heterocyclic compounds; homodromic domains; hydrogen bonding; nitroimidazoles; Organic compounds; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Five membered ring; Stacking sequence; Molecular structure; Centrosymmetry test; Nitrogen heterocycle; Nitro compounds; XRD; Experimental study; Hydrogen bonds; Ambient temperature; Six membered ring; Temperature range 65-273 K; Organic compounds; Low temperature; Hydrates; Oxygen nitrogen heterocycle; Crystal structure
• ISSN: 0108-7681; 1600-5740
• DOI: 10.1107/S010876810301070X

The compound studied is 1,2‐dimethyl‐4‐nitro‐5‐morpholino­imidazole (1) in its anhydrous (1) and hydrated [(1)·H2O] 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)·H2O. 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)·H2O 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.