Control of chiroptical properties of axially chiral naphthalene oligomers

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Abstract

We developed several naphthalene oligomers with contiguous chiral axes as chiroptical dyes. RS-alternating oligomers with the 2, 2′-methylenedioxy bridges take a V-shaped conformation with a notably extensive conjugation in the rod direction, leading to high fluorescence in solution and in the solid state (ΦFL, solution = 0.64 and ΦFLsolid = 0.13 for an octamer). Theoretical studies indicated that the dihedral angles of naphthalene rings were held steady 48-49°, and both the HOMO and LUMO were spread throughout the molecule. It should be noted that the bridged R,R,R,R,R,R,R)-naphthalene octamer showed more intense fluorescence (FL) and circularly polarized luminescence (CPL) (ΦFL, solution = 0.90, g lum, solution = + 2.2 × 10-3, ΦFL, solid = 0.22, and g lum, solid = + 7.0 × 10-3). The high ΦFL and glum values were due to the rigidity. Moreover, the octamer molecules were incapable of forming efficiently stacked structures due to the non-planar conformation, which led to a high ΦFL solid value in the solid state. A(R,R, R)-naphthalene tetramer possessing eight pyrenes displayed intense excimer-FL and CPL (ΦFLsolution = 0.25, glum, solution = + 0.034, ΦFL, solid = 0.28, and g lum, solid = +5.3 × 10-3). Pyrenes densely connected to a naphthalene tetramer via ester linkers were conformationally rigid with right-handed chirality and were important for obtaining strong CPL.

Original languageEnglish
Pages (from-to)885-893
Number of pages9
JournalYuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry
Volume76
Issue number9
DOIs
Publication statusPublished - Jan 1 2018

Keywords

  • Absorption
  • Axial chirality
  • Bottom-up synthesis
  • Circular dichroism
  • Circularly polarized luminescence
  • Conjugation
  • Fluorescence
  • Helical structure
  • Naphthalene

ASJC Scopus subject areas

  • Organic Chemistry

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