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Four polymorphs (polytypes) of 5,6-dimethylbenzofurazan 1-oxide
Doyle Britton1, Victor G Young, Wayland E Noland
1Department of Chemistry, University of Minnesota, Minneapolis, MN 55455-0431, USA. britton@umn.edu
Acta Crystallographica. Section B, Structural Science
|September 21, 2012
Summary
Four polymorphic forms of 5,6-Dimethylbenzofurazan 1-oxide (Me2BF) were identified. These polytypes exhibit molecular disorder and specific layer interactions, including allotwining between polymorphs.
Area of Science:
- Crystallography
- Solid-state chemistry
Background:
- Polymorphism is common in organic compounds.
- Understanding crystal structures is crucial for material properties.
Purpose of the Study:
- To characterize the polymorphic forms of 5,6-Dimethylbenzofurazan 1-oxide (Me2BF).
- To investigate the molecular arrangement and intermolecular interactions within each polymorph.
- To identify and describe instances of allotwining between different polymorphs.
Main Methods:
- Single-crystal X-ray diffraction was used to determine the crystal structures.
- Analysis of molecular packing and intermolecular interactions (C-H···N, C-H···O).
- Identification of twinning and allotwining phenomena.
Main Results:
- Four distinct polymorphic forms of Me2BF were discovered, all related as polytypes.
- Each polymorph features disordered molecules arranged in head-to-tail ribbons forming planar layers.
- Weak C-H···N and C-H···O interactions stabilize the layers, with variations in inter-layer contacts.
- Allotwining, or oriented overgrowth between different polymorphs, was observed in four instances.
Conclusions:
- 5,6-Dimethylbenzofurazan 1-oxide (Me2BF) exhibits complex polymorphism.
- The crystal structures are characterized by molecular disorder and specific ribbon/layer arrangements.
- Intermolecular interactions and allotwining play significant roles in the solid-state behavior of Me2BF.
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