Temperature-dependent polymorphism of N-(4-fluorophenyl)-1,5-dimethyl-1H-imidazole-4-carboxamide 3-oxide: experimental and theoretical studies on intermolecular interactions in the crystal state |
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Authors: | Agnieszka J Rybarczyk-Pirek Marlena ?ukomska Krzysztof Ejsmont Marcin Jasiński Marcin Palusiak |
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Institution: | 1. Structural Chemistry and Crystallography Group, Department of Theoretical and Structural Chemistry, University of ?ód?, ul. Pomorska 163/165, 90-236, Lodz, Poland 2. Faculty of Chemistry, University of Opole, ul. Oleska 48, 45-052, Opole, Poland 3. Department of Organic and Applied Chemistry, University of ?ód?, ul. Tamka 12, 91-403, Lodz, Poland
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Abstract: | X-ray analysis of N-(4-fluorophenyl)-1,5-dimethyl-1H-imidazole-4-carboxamide 3-oxide reveals the temperature-dependent polymorphism associated with the crystallographic symmetry conversion. The observed crystal structure transformation corresponds to a symmetry reduction from I41 /a (I) to P43 (II) space groups. The phase transition mainly concerns the subtle but clearly noticeable reorganization of molecules in the crystal space, with the structure of individual molecules left almost unchanged. The Hirshfeld surface analysis shows that various intermolecular contacts play an important role in the crystal packing, revealing graphically the differences in spatial arrangements of the molecules in both polymorphs. The N-oxide oxygen atom acts as a formally negatively charged hydrogen bonding acceptor in intramolecular hydrogen bond of N–H…O? type. The combined crystallographic and theoretical DFT methods demonstrate that the observed intramolecular N-oxide N–H…O hydrogen bond should be classified as a very strong charge-assisted and closed-shell non-covalent interaction. |
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