Thiophene-Based Double Helices: Syntheses, X-ray Structures, and Chiroptical Properties

Sheng Zhang, Xinming Liu, Chunli Li, Lu Li, Jinsheng Song, Jianwu Shi, Martha Morton, Suchada Rajca, Andrzej Rajca, Hua Wang

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

We demonstrate facile and efficient construction of conjugated double helical ladder oligomers from the saddle-shaped cyclooctatetrathiophene (COTh) building blocks. The key step involves deprotonation of tetra[3,4]thienylene (β,β-COTh) with n-BuLi which displays remarkably high ipsilateral selectivity. Three racemic double helical ladder oligomers, rac-DH-1, rac-DH-2, and rac-DH-3, containing two, three, and five COTh annelated moieties are efficiently synthesized by diastereoselective coupling of the racemic precursors. The X-ray crystallographic studies of rac-DH-1, rac-DH-2 and rac-DH-3 unambiguously revealed that each double helical scaffold has two single helices intertwined with each other via the C-C single bonds. Following removal of TMS groups, double helical ladder oligomer rac-DH-1-D had sufficient solubility to be resolved via chiral HPLC, thus enabling determination of its chirooptical properties such as CD spectra and optical rotation. (+)-DH-1-D has a large barrier for racemization, with lower limit of ΔG > 48 kcal mol-1, which may be compared to DFT-computed barrier of 51 kcal mol-1. The enantiomers of DH-1-D show 1 order of magnitude stronger chirooptical properties than the carbon-sulfur [7]helicene, as determined by the anisotropy factor g = Δϵ/ϵ = -0.039, based on Δϵmax = -11 and ϵ = 2.8 × 102 L mol-1 cm-1 in cyclohexane at 327 nm.

Original languageEnglish (US)
Pages (from-to)10002-10010
Number of pages9
JournalJournal of the American Chemical Society
Volume138
Issue number31
DOIs
StatePublished - Aug 10 2016

Fingerprint

Optical Rotation
Thiophenes
Anisotropy
Ladders
Thiophene
Sulfur
Oligomers
Solubility
Carbon
High Pressure Liquid Chromatography
X-Rays
X rays
Optical rotation
Deprotonation
Enantiomers
Cyclohexane
Discrete Fourier transforms
Scaffolds
n-butyllithium
single bond

ASJC Scopus subject areas

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

Cite this

Thiophene-Based Double Helices : Syntheses, X-ray Structures, and Chiroptical Properties. / Zhang, Sheng; Liu, Xinming; Li, Chunli; Li, Lu; Song, Jinsheng; Shi, Jianwu; Morton, Martha; Rajca, Suchada; Rajca, Andrzej; Wang, Hua.

In: Journal of the American Chemical Society, Vol. 138, No. 31, 10.08.2016, p. 10002-10010.

Research output: Contribution to journalArticle

Zhang, Sheng ; Liu, Xinming ; Li, Chunli ; Li, Lu ; Song, Jinsheng ; Shi, Jianwu ; Morton, Martha ; Rajca, Suchada ; Rajca, Andrzej ; Wang, Hua. / Thiophene-Based Double Helices : Syntheses, X-ray Structures, and Chiroptical Properties. In: Journal of the American Chemical Society. 2016 ; Vol. 138, No. 31. pp. 10002-10010.
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