220347-95-5Relevant academic research and scientific papers
Synthesis and aggregation of a conjugated helical molecule
Nuckolls, Colin,Katz, Thomas J.,Katz, Gail,Collings, Peter J.,Castellanos, Louis
, p. 79 - 88 (1999)
Described are an improved method to synthesize helicenebisquinone 1 and an efficient method to resolve its enantiomers and those of other helicenebisquinones by separating derived camphanate esters. The union of p- benzoquinone and the bis(triisopropylsilylenol ether) of a 2,7-diacetyl-4,5- dialkoxynaphthalene gives the helicene skeleton in 56% yield. Molecules of nonracemic 1 aggregate when their dodecane solutions are concentrated to 5 x 10-4 M or more. Chloroform dissociates the aggregates. Aggregation is characterized by enhanced 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 that shift to the red, 1H NMR resonances that shift upfield, and organization of the pure material into fibers. The CD and UV-vis absorption spectra of spin-coated films are similar to those of concentrated solutions in dodecane, but the g values are higher. The specific rotation of a cast film, [α](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 give concentrated solutions in dodecane. Also nonracemic helicene 3 does not show the characteristics of aggregation either in solution or in bulk.
