Different molecular conformations in the crystal structures of three 5-nitroimidazolyl derivatives

Luis F. B. Osorio, Samir A Carvalho, Edson F. da Silva, Carlos A. M. Fraga, Solange M. S. V. Wardell, Bruce F. Milne, James L Wardell, William T A Harrison

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Abstract

The crystal structures of (E)-1-methyl-5-nitro-1H-imidazole-2-carbaldehyde O-benzyl­oxime, C12H12N4O3, (I), (E)-1-methyl-5-nitro-1H-imidazole-2-carb­alde­hyde O-(4-fluoro­benz­yl) oxime, C12H11FN4O3, (II), and (E)-1-methyl-5-nitro-1H-imidazole-2-carbaldehyde O-(4-bromo­benz­yl) oxime, C12H11BrN4O3, (III), are described. The dihedral angle between the ring systems in (I) is 49.66 (5)° and the linking Nm—C—C=N (m = methyl­ated) bond shows an anti conformation [torsion angle = 175.00 (15)°]. Compounds (II) and (III) are isostructural [dihedral angle between the aromatic rings = 8.31 (5)° in (II) and 5.34 (15)° in (III)] and differ from (I) in showing a near-syn conformation for the Nm—C—C=N linker [torsion angles for (II) and (III) = 17.64 (18) and 8.7 (5)°, respectively], which allows for the occurrence of a short intra­molecular C—H...N contact. In the crystal of (I), C—H...N hydrogen bonds link the mol­ecules into [010] chains, which are cross-linked by very weak C—H...O bonds into (100) sheets. Weak aromatic π–π stacking inter­actions occur between the sheets. The extended structures of (II) and (III) feature several C—H...N and C—H...O hydrogen bonds, which link the mol­ecules into three-dimensional networks, which are consolidated by aromatic π–π stacking inter­actions. Conformational energy calculations and Hirshfeld fingerprint analyses for (I), (II) and (III) are presented and discussed.
Original languageEnglish
Pages (from-to)380-384
Number of pages5
JournalActa Crystallographica Section E: Structure Reports Online
VolumeE74
Issue number3
Early online date23 Feb 2018
DOIs
Publication statusPublished - 1 Mar 2018

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Keywords

  • benzoxa­thiol-2-one
  • hydrogen bonds
  • Hirshfeld surface
  • crystal structure

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