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An aza-cyclophane stacked in racemic columnar assemblies: whole-molecule disorder in a two-dimensional solid solution
Matthias Zeller1, Marlon R Lutz, Daniel P Becker
1Youngstown State University, Department of Chemistry, 1 University Plaza, Youngstown, OH 44555-3663, USA. mzeller@cc.ysu.edu
Acta Crystallographica. Section B, Structural Science
|March 21, 2009
Summary
A Beckmann rearrangement of a cyclotriveratrylene (CTV) derivative yielded a macrocyclic amide. This molecule forms unusual columnar assemblies with alternating enantiomers, creating a 2D solid solution and molecular disorder.
Area of Science:
- Supramolecular Chemistry
- Crystal Engineering
- Organic Synthesis
Background:
- Cyclotriveratrylene (CTV) derivatives are known for their unique structural properties.
- Macrocyclic amides offer diverse applications in host-guest chemistry and materials science.
- Understanding molecular disorder in crystalline solids is crucial for predicting material properties.
Purpose of the Study:
- To synthesize and characterize a novel macrocyclic amide derived from a CTV oxime.
- To investigate the crystal structure and self-assembly behavior of the synthesized macrocycle.
- To explore the phenomenon of molecular disorder and symmetry changes in crystalline columnar assemblies.
Main Methods:
- Ring expansion of a CTV oxime derivative via Beckmann rearrangement.
- Single-crystal X-ray diffraction analysis to determine molecular and crystal structure.
- Analysis of crystallographic data to identify molecular arrangements and disorder.
Main Results:
- Successful synthesis of a ten-membered N-acetyl macrocyclic amide.
- Crystallization as a chloroform monosolvate, forming columnar assemblies.
- Observation of unusual whole-molecule disorder and a two-dimensional solid solution due to alternating D and L enantiomers in adjacent columns, leading to a symmetry change from Pna2(1) to Pnma.
Conclusions:
- The Beckmann rearrangement provides a viable route to CTV-derived macrocyclic amides.
- The macrocycle exhibits complex self-assembly, forming racemic columns that pack into a higher-symmetry space group.
- This study highlights the interplay between molecular chirality, self-assembly, and emergent crystallographic symmetry in ordered materials.
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