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Solvent-dependent polymorphism in isomeric N-(nitrobenzylidene)iodoanilines
George Ferguson1, Christopher Glidewell, John N Low
1School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland.
Summary
Crystallization solvents influence the solid-state structures of nitrobenzylidene iodoaniline isomers. Different solvents yield distinct polymorphs with varied molecular arrangements and intermolecular interactions, impacting crystal packing.
Area of Science:
- Solid-state chemistry
- Crystallography
- Organic chemistry
Background:
- Isomeric compounds can exhibit different solid-state behaviors.
- Solvent choice is critical in controlling polymorphism.
- Understanding crystal structures informs material properties.
Purpose of the Study:
- To investigate the influence of crystallization solvent (acetone vs. ethanol) on the polymorphism of N-(nitrobenzylidene)iodoaniline isomers.
- To characterize the distinct crystal structures and intermolecular interactions of different polymorphs.
- To elucidate the role of specific interactions (e.g., iodo-nitro, pi-pi stacking, hydrogen bonding) in stabilizing crystal packing.
Main Methods:
- Single-crystal X-ray diffraction was employed to determine the molecular and crystal structures.
- Analysis of intermolecular interactions, including hydrogen bonds and halogen bonds, was performed.
- Comparison of polymorphs obtained from different crystallization solvents.
Main Results:
- Three isomeric N-(nitrobenzylidene)iodoanilines yielded different polymorphs when crystallized from acetone compared to ethanol.
- The second polymorph of 2-iodo-N-(2-nitrobenzylidene)aniline showed molecular disorder in space group C2/c without specific directional interactions.
- The second polymorph of 2-iodo-N-(3-nitrobenzylidene)aniline featured a different molecular conformation and was stabilized by iodo-nitro and pi-pi stacking interactions.
- The second polymorph of 3-iodo-N-(2-nitrobenzylidene)aniline (Z'=2, P2(1)) exhibited sheet structures formed by C-H...O and C-H...pi(arene) hydrogen bonds.
Conclusions:
- Solvent-dependent polymorphism is significant for N-(nitrobenzylidene)iodoaniline isomers.
- Intermolecular interactions, including halogen bonding and hydrogen bonding, dictate the formation of specific polymorphs and their supramolecular architectures.
- The study highlights the complexity of crystal engineering for these compounds.