Functionalized thiophene-based [7]helicene: Chirooptical properties versus electron delocalization

Andrzej Rajca, Maren Pink, Shuzhang Xiao, Makoto Miyasaka, Suchada Rajca, Kausik Das, Kristin Plessel

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(Chemical Equation Presented) The functionalized, enantiomerically pure [7]helicene 1 derived from bis(benzodithiophene) functionalized with four heptyl groups is prepared from 1,8-dibromo-4,5-diheptylbenzo[1,2-b:4,3-b′] dithiophene building block 2. Such [7]helicene structure, functionalized with bromines at the terminal positions of the helicene inner rim and multiple solubilizing alkyl groups, is an attractive building block for long [n]helicenes and oligo[7]helicenes. Chirooptical properties and the degree of electron delocalization are determined and compared to those of analogous carbon-sulfur [7]helicene and [7]helicenes derived from benzodithiophene to provide a correlation between chirooptical properties and the degree of electron delocalization. [7]Helicene 1 possesses amoderately increased electron delocalization, but its chirooptical properties are similar to those for analogous [7]helicenes with relatively lower electron delocalization, indicating that chirooptical properties are not significantly affected by electron delocalization for this series of [7]helicenes. Molecular structures of racemic [7]helicene 1 and its benzodithiophene building block 2 are confirmed by single-crystal X-ray analysis. Crystals of 2 are chiral and adopt the shape of long, flexible, flat needles that can be readily bent.

Original languageEnglish (US)
Pages (from-to)7504-7513
Number of pages10
JournalJournal of Organic Chemistry
Issue number19
StatePublished - Oct 2 2009
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry


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