Two-component fibers/gels and vesicles formed from hetero-double-helices of pseudoenantiomeric ethynylhelicene oligomers with branched side chains

Nozomi Saito, Masanori Shigeno, Masahiko Yamaguchi

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

A methodology for the formation of fibers/gels and vesicles by molecular assembly and for controlling their properties is presented. Two-component systems of pentamer (P)-5 and tetramer (M)-4 pseudoenantiomeric ethynylhelicenes with decyloxycarbonyl (D) and 4-methyl-2-(2-methylpropyl)-1-pentyloxycarbonyl (bD) side-chains have been examined. Distinct aggregates were formed by changing the solvent for the three combinations of (P)-bD-5/(M)-bD-4, (P)-D-5/(M)-bD-4, and (P)-D-5/(M)-D-4. In toluene, (P)-bD-5/(M)-bD-4, (P)-D-5/(M)-bD-4, and (P)-D-5/(M)-D-4 all formed gels and fibrous assemblies were observed by AFM. The minimum gel-forming concentration (MGC) decreased in the order (P)-bD-5/(M)-bD-4>(P)-D-5/(M)-bD-4>(P)-D-5/(M)-D-4. In diethyl ether, vesicular formation was observed by dynamic light scattering (DLS), AFM, and TEM, and the size of the vesicles decreased in the order (P)-bD-5/(M)-bD- 4>(P)-D-5/(M)-bD-4>(P)-D-5/(M)-D-4. Both fiber/gel and vesicle formation were accompanied by enhanced CDs and redshifted UV/Vis absorption bands with a change in color to deep yellow. These are novel two-component oligomeric systems that form assemblies of fibers/gels or vesicles depending on the solvent, and the structures and properties of the assemblies can be fine-tuned by changing the combination of oligomers. In m-difluorobenzene, a homogeneous solution was obtained with (P)-D-5/(M)-bD-4, which again exhibits enhanced CDs and redshifted UV/Vis absorptions. Vapor pressure osmometry analysis showed the formation of a bimolecular heteroaggregate. The study has indicated that pseudoenantiomeric oligomers form hetero-double-helices that hierarchically assemble to form fibers/gels and vesicles.

Original languageEnglish
Pages (from-to)8994-9004
Number of pages11
JournalChemistry - A European Journal
Volume18
Issue number29
DOIs
Publication statusPublished - 2012 Jul 16

Keywords

  • gels
  • helical structures
  • helicenes
  • self-assembly
  • vesicles

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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