Sequential self-catalytic reactions in the formation of hetero-double-helix and their self-assembled gels by pseudoenantiomer mixtures of ethynylhelicene oligomers

Tsukasa Sawato, Masahiko Yamaguchi

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

A 1:1 mixture of pseudoenantiomer ethynylhelicene (P)-pentamer and (M)-tetramer in toluene formed hetero-double-helix and their self-assembled gels. Kinetic analysis under isothermal conditions showed a complex nonlinear nature with regard to temperature changes. At 60°C, sigmoidal kinetics were observed, which disappeared after seeding with the self-assembled gels. These findings indicate the involvement of self-catalytic reaction I, in which a hetero-double-helix catalyzes the reaction to form a hetero-double-helix from random-coils. At 20°C, stairwise biphasic kinetics were observed, which disappeared after seeding. This phenomenon was explained by the involvement of two reactions with sigmoidal kinetics, namely, the formation of self-assembled gel I from hetero-double-helix by self-catalytic reaction II and the formation of self-assembled gel II by self-catalytic reaction III. Constant-rate temperature change experiments between 90 and 5°C showed nonsigmoidal thermal hysteresis in accordance with the involvement of sequential self-catalytic reactions with different reaction rates.

Original languageEnglish
Pages (from-to)824-832
Number of pages9
JournalChirality
Volume32
Issue number6
DOIs
Publication statusPublished - 2020 Jun 1

Keywords

  • helicene oligomer
  • hetero-double-helix
  • self-assembly
  • sequential self-catalytic reactions
  • stairwise biphasic kinetics

ASJC Scopus subject areas

  • Analytical Chemistry
  • Catalysis
  • Pharmacology
  • Drug Discovery
  • Spectroscopy
  • Organic Chemistry

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