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Three isomeric bis(methoxycarbonyl)[2.2]paracyclophanes
Peter G Jones1, Jörg Hillmer, Henning Hopf
1Institut für Anorganische und Analytische Chemie, Technische Universität Braunschweig, Postfach 3329, 38023 Braunschweig, Germany. jones@xray36.anchem.nat.tu-bs.de
Summary
This study details three isomers of bis(methoxycarbonyl)[2.2]paracyclophane, analyzing their structural features and crystal packing. The findings reveal typical paracyclophane characteristics and specific intermolecular interactions, including C-H.pi and hydrogen bonds.
Area of Science:
- Organic Chemistry
- Crystallography
- Supramolecular Chemistry
Background:
- [2.2]Paracyclophanes are macrocyclic compounds known for their unique structural and electronic properties.
- Understanding the conformational preferences and intermolecular interactions of substituted paracyclophanes is crucial for designing novel materials.
- Methoxycarbonyl substituents introduce specific electronic and steric effects that influence molecular packing.
Purpose of the Study:
- To synthesize and characterize three title isomers of bis(methoxycarbonyl)[2.2]paracyclophane: 4,16- (pseudo-ortho), 4,15- (pseudo-gem), and 4,12- (pseudo-para).
- To investigate the typical structural features of [2.2]paracyclophanes in these isomers, including ring conformation, bond lengths, and angles.
- To analyze the crystal packing of the isomers, focusing on intermolecular interactions such as C-H.pi and hydrogen bonds.
Main Methods:
- Synthesis of bis(methoxycarbonyl)[2.2]paracyclophane isomers.
- Single-crystal X-ray diffraction analysis to determine molecular structures and crystal packing.
- Analysis of geometric parameters (bond lengths, angles, dihedral angles) and intermolecular interactions.
Main Results:
- All three isomers exhibit characteristic [2.2]paracyclophane structural features: flattened boat conformation, elongated bridge bonds, and narrow bridgehead angles.
- The 4,12-isomer possesses crystallographic inversion symmetry.
- Carbonyl groups are oriented away from the aromatic rings, widening the angle at the ring substituent atom; C-H.pi interactions are observed in the 4,15-isomer, while C-H.O hydrogen bonds are present in the 4,16- and 4,12-isomers.
Conclusions:
- The study confirms the typical structural motifs of [2.2]paracyclophanes in the synthesized isomers.
- The orientation of carbonyl groups and the specific intermolecular interactions (C-H.pi and C-H.O hydrogen bonds) play a significant role in the crystal packing of these compounds.
- These findings contribute to the understanding of structure-property relationships in substituted paracyclophanes.