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Molecular recognition and self-assembly special feature: Self-assembly of dimeric tetraurea calix[4]pyrrole capsules.

ABSTRACT: Calix[4]pyrroles having extended aromatic cavities have been functionalized with 4 ureas in the para position of their meso phenyl substituents. This elaboration of the upper rim was completed in 2 synthetic steps starting from the alpha,alpha,alpha,alpha-tetranitro isomer of the calix[4]pyrrole obtained in the acid catalyzed condensation of p-nitrophenyl methyl ketone and pyrrole. In dichloromethane solution and in the presence of 4,4'-bipyridine N-N'-dioxide the tetraurea calix[4]pyrrole dimerizes reversibly forming a cyclic array of 16 hydrogen bonds and encapsulating 1 molecule of bis-N-oxide. The encapsulated guest is bound in the cavity by hydrogen bonding to the 2 endohedral calix[4]pyrrole centers. Further evidence for dimerization of the tetraurea calix[4]pyrroles is provided by (1)H-NMR experiments and by the formation of mixed capsules.

SUBMITTER: Ballester P

PROVIDER: S-EPMC2705570 | biostudies-literature | 2009 Jun

REPOSITORIES: biostudies-literature

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Molecular recognition and self-assembly special feature: Self-assembly of dimeric tetraurea calix[4]pyrrole capsules.

Ballester Pablo P Gil-Ramírez Guzmán G

Proceedings of the National Academy of Sciences of the United States of America 20090304 26

Calix[4]pyrroles having extended aromatic cavities have been functionalized with 4 ureas in the para position of their meso phenyl substituents. This elaboration of the upper rim was completed in 2 synthetic steps starting from the alpha,alpha,alpha,alpha-tetranitro isomer of the calix[4]pyrrole obtained in the acid catalyzed condensation of p-nitrophenyl methyl ketone and pyrrole. In dichloromethane solution and in the presence of 4,4'-bipyridine N-N'-dioxide the tetraurea calix[4]pyrrole dimer ...[more]

PMID: 19261848

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