Helical ribbon aggregate composed of a crown-appended cholesterol derivative which acts as an amphiphilic gelator of organic solvents and as a template for chiral silica transcription

Hwa Jung Jong Hwa Jung, H. Kobayashi, M. Masuda, T. Shimizu, S. Shinkai

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285 Citations (Scopus)

Abstract

New crown-appended cholesterol-based organogelator 1, which has two cholesterol skeletons as a chiral aggregate-forming site, two amino groups as an acidic proton-binding site, and one crown moiety as a cation-binding site, was synthesized, and the gelation ability was evaluated in organic solvents. It can gelate acetic acid, acetonitrile, acetone, ethanol, 1-butanol, 1-hexanol, DMSO, and DMF under 1.0 wt %, indicating that 1 acts as a versatile gelator of various organic solvents. To characterize the aggregation mode in the organogel system, we observed a CD spectrum of the acetic acid gel 1. In the CD spectrum, the λθ=0 value appears at 353 nm, which is the same as the absorption maximum λmax = 353 nm. The positive sign for the first Cotton effect indicates that the dipole moments of azobenzene chromophores tend to orient in a clockwise direction. Very surprisingly, the TEM images of the 1 + acetic acid gel resulted in the helical ribbon and the tubular structures. Sol-gel polymerization of tetraethoxysilane was carried out using 1 in the gel phase. The silica obtained from the 1 + acetic acid gel showed the helical ribbon with 1700-1800-nm pitches and the tubular structure of the silica with ∼560-nm outer diameter. As far as can be recognized, all the helicity possesses a right-handed helical motif. Since the exciton-coupling band of the organogel also shows R (right-handed) helicity, we consider that a microscopic helicity is reflected by a macroscopic helicity.

Original languageEnglish
Pages (from-to)8785-8789
Number of pages5
JournalJournal of the American Chemical Society
Volume123
Issue number36
DOIs
Publication statusPublished - Sep 12 2001
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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