Synthesis and Aggregation of a Conjugated Helical Molecule
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- 作者：Colin Nuckolls ; Thomas J. Katz ; Gail Katz ; Peter J. Collings ; and Louis Castellanos
- 刊名：Journal of the American Chemical Society
- 出版年：1999
- 出版时间：January 13, 1999
- 年：1999
- 卷：121
- 期：1
- 页码：79 - 88
- 全文大小：334K
- 年卷期：v.121,no.1(January 13, 1999)
- ISSN：1520-5126
文摘
Described are an improved method to synthesize helicenebisquinone 1 and an efficient method toresolve its enantiomers and those of other helicenebisquinones by separating derived camphanate esters. Theunion of p-benzoquinone and the bis(triisopropylsilylenol ether) of a 2,7-diacetyl-4,5-dialkoxynaphthalene givesthe helicene skeleton in 56% yield. Molecules of nonracemic 1 aggregate when their dodecane solutions areconcentrated to 5 × 10-4 M or more. Chloroform dissociates the aggregates. Aggregation is characterized byenhanced circular dichroisms and g values, red-shifted UV-vis absorptions, increased specific rotations,increased light scattering at an absorption frequency, and, as reported previously, fluorescence emissions thatshift to the red, 1H NMR resonances that shift upfield, and organization of the pure material into fibers. TheCD and UV-vis absorption spectra of spin-coated films are similar to those of concentrated solutions indodecane, but the g values are higher. The specific rotation of a cast film, [
]D, is 158 000 (deg cm2)/10 g.Unlike the nonracemic material, the racemic in bulk does not form visible fibers and is too insoluble to giveconcentrated solutions in dodecane. Also nonracemic helicene 3 does not show the characteristics of aggregationeither in solution or in bulk.
]D, is 158 000 (deg cm2)/10 g.Unlike the nonracemic material, the racemic in bulk does not form visible fibers and is too insoluble to giveconcentrated solutions in dodecane. Also nonracemic helicene 3 does not show the characteristics of aggregationeither in solution or in bulk.