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Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Zinc-[7]helicenocyanine and Its Discrete π-Stacked Homochiral Dimer
Fangyuan Zhang1, Krzysztof Radacki2, Holger Braunschweig2
1Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
Abstract:
In this communication, we demonstrate a novel approach to prepare a discrete dimer of chiral phthalocyanine (Pc) by exploiting the flexible molecular geometry of helicenes, which enables structural interlocking and strong aggregation tendency of Pcs. Synthesized [7]helicene-Pc hybrid molecular structure, zinc-[7]helicenocyanine (Zn-7HPc), exclusively forms a stable dimeric pair consisting of two homochiral molecules. The dimerization constants were estimated to be as high as 8.96×106 M-1 and 3.42×107 M-1 in THF and DMSO, respectively, indicating remarkable stability of dimer. In addition, Zn-7HPc exhibited chiral self-sorting behavior, which resulted in preferential formation of a homochiral dimer also in the racemic sample. Two phthalocyanine subunits in the dimeric form strongly communicate with each other as revealed by a large comproportionation constant and observation of an IV-CT band for the thermodynamically stable mixed-valence state.
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