Two new polytypes of 2,4,6-tri-bromo-benzo-nitrile

Area of Science:

• Solid-state chemistry
• Crystallography
• Organic chemistry

Background:

• Polymorphism is common in organic compounds, influencing their physical and chemical properties.
• Understanding crystal structures is crucial for material science and drug development.
• Previous studies by Carter & Britton characterized some forms of tri-bromo-benzonitrile.

Purpose of the Study:

• To investigate and characterize novel polymorphs of 2,4,6-tri-bromo-benzonitrile (RCN).
• To re-examine the crystal structure of 1,3,5-tri-bromo-2-iso-cyano-benzene (RNC).
• To explore the polytypic relationships between different crystalline forms of RCN and RNC.

Main Methods:

• Single-crystal X-ray diffraction was used to determine the unit cells and atomic arrangements.
• Analysis of intermolecular interactions, specifically C-N···Br contacts, was performed.
• Comparison of crystal structures to identify polytypic relationships and isostructural compounds.

Main Results:

• Three polymorphs of RCN were identified, two of which are novel, all exhibiting layer structures with variations in stacking.
• The layers in RCN polymorphs are assembled via C-N···Br contacts forming R(2)2(10) rings.
• 1,3,5-tri-bromo-2-iso-cyano-benzene (RNC) was found to be isostructural with one of the novel RCN polymorphs.

Conclusions:

• The study reveals new polytypes of RCN, highlighting the complexity of its solid-state forms.
• The identified intermolecular interactions play a key role in stabilizing the observed layer structures.
• The isostructural relationship between RNC and an RCN polymorph provides further insight into structure-property correlations.