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m-Diethynylbenzene macrocycles: syntheses and self-association behavior in solution.
Yoshito Tobe1, Naoto Utsumi, Kazuya Kawabata
1Department of Chemistry, Faculty of Engineering Science, Osaka University, and CREST, Japan. tobe@chem.es.osaka-u.ac.jp
Journal of the American Chemical Society
|May 9, 2002
Summary
m-Diethynylbenzene macrocycles (DBMs) were synthesized and their self-association behavior studied. DBMs show unique aggregation in solvents, enhanced by nucleation and macrocyclic structure, leading to stronger pi-pi stacking than related compounds.
Area of Science:
- Supramolecular Chemistry
- Organic Synthesis
- Materials Science
Background:
- Macrocyclic compounds offer unique structural and functional properties.
- Understanding self-assembly is crucial for designing advanced materials.
- Diethynylbenzene macrocycles (DBMs) represent a novel class of cyclic molecules.
Purpose of the Study:
- To synthesize m-diethynylbenzene macrocycles (DBMs) with varying side chains.
- To investigate the self-association behavior of DBMs in different solvents.
- To elucidate the influence of macrocyclic structure on aggregation properties.
Main Methods:
- Synthesis of cyclic tetramers, hexamers, and octamers of DBMs via oxidative coupling or intramolecular cyclization.
- Investigation of aggregation properties using 1H NMR spectroscopy and vapor pressure osmometry (VPO).
- Comparative analysis with acyclic oligomers and related phenylacetylene macrocycles.
Main Results:
- DBMs exhibit unique aggregation behavior in solvents like acetone and toluene, with a nucleation mechanism enhancing association.
- Aggregation is stronger in polar solvents due to solvophobic effects and in aromatic solvents due to pi-pi stacking.
- Hexameric DBMs with large cavities show particularly high association constants in aromatic solvents.
- DBMs aggregate more readily than phenylacetylene macrocycles due to electron-withdrawing butadiyne linkages.
Conclusions:
- The macrocyclic structure significantly influences the self-aggregation propensity of DBMs.
- DBMs demonstrate tunable aggregation behavior dependent on solvent polarity and aromaticity.
- The butadiyne linkage in DBMs enhances pi-pi stacking interactions, promoting self-association.
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