Deterministic and Stochastic Chiral Symmetry Breaking Exhibited by Racemic Aminomethylenehelicene Oligomers

Racemic mixtures of aminomethylenehelicene (P)‐ and (M)‐pentamers exhibited deterministic and stochastic chiral symmetry breaking during hetero‐double‐helix formation and self‐assembly in solution. Heating a 50:50 mixture of (P)‐ and (M)‐pentamers at 90 °C, and then cooling the mixture to 70 °C resu...

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Published inChemistry : a European journal Vol. 23; no. 2; pp. 327 - 333
Main Authors Kushida, Yo, Sawato, Tsukasa, Shigeno, Masanori, Saito, Nozomi, Yamaguchi, Masahiko
Format Journal Article
LanguageEnglish
Published Germany Wiley Subscription Services, Inc 05.01.2017
Subjects
Broken symmetry
chiral symmetry breaking
circular dichroism
Coiling
Cooling effects
Cotton
double helix
Formations
Heating
helicenes
Self assembly
Stochasticity
Symmetry
self-assembly
chiral symmetry breaking
circular dichroism
helicenes
double helix
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Summary:Racemic mixtures of aminomethylenehelicene (P)‐ and (M)‐pentamers exhibited deterministic and stochastic chiral symmetry breaking during hetero‐double‐helix formation and self‐assembly in solution. Heating a 50:50 mixture of (P)‐ and (M)‐pentamers at 90 °C, and then cooling the mixture to 70 °C resulted in hetero‐double‐helix formation; a Cotton effect with negative Δε at λ=315 nm appeared. Chiral self‐assembly occurred when the mixture was cooled to 25 °C. A strong tendency of deterministic chiral symmetry breaking appeared at the molecular and self‐assembled levels, which was indicated by the negative Δε at λ=315 nm that appeared in most cases in repeated experiments. Mixtures containing 60:40 and 40:60 (P)‐/(M)‐pentamers also self‐assembled with the same chirality. When a homo‐double‐helix (P)‐/(M)‐pentamer and a random coil (M)‐/(P)‐pentamer were mixed, the chiral self‐assembly formed stochastically, and heating and cooling resulted in deterministic chiral symmetry breaking. Racemic to chiral: Racemic mixtures of aminomethylenehelicene (P)‐ and (M)‐pentamers exhibited deterministic and stochastic chiral symmetry breaking during hetero‐double‐helix formation and self‐assembly in solution (see figure). Racemic mixtures prepared by mixing a random coil and a homo‐double‐helix exhibited stochastic chiral self‐assembly.
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content type line 23
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201601792