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Spatially Heterogeneous Nature of Self‐Catalytic Reaction in Hetero‐Double Helix Formation of Helicene Oligomers
Author(s) -
Kushida Yo,
Sawato Tsukasa,
Saito Nozomi,
Shigeno Masanori,
Satozono Hiroshi,
Yamaguchi Masahiko
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201600627
Subject(s) - pentamer , chemistry , helicene , circular dichroism , catalysis , helix (gastropod) , tetramer , homogeneous , crystallography , absorption (acoustics) , porphyrin , photochemistry , materials science , molecule , organic chemistry , thermodynamics , ecology , biochemistry , enzyme , physics , snail , composite material , biology
A 1:1 mixture of pseudoenantiomeric aminomethylenehelicene oligomers, ( P )‐tetramer and ( M )‐pentamer, in fluorobenzene show a self‐catalytic phenomenon in the formation of hetero‐double helices from random coils. This study visualizes the spatially heterogeneous nature of the self‐catalytic reaction in dilute solution. UV/Vis imaging analysis of the mixture at 70 °C, containing random coils, exhibits a homogeneous bright area. When the solution is cooled from 70 to 30 °C and held at that temperature, dark domains of approximately 1 mm in size appear, which move approximately at a rate of 1 mm min −1 . The dark domains indicate that weaker UV/Vis absorption results from the formation of hetero‐double helices, which is supported by circular dichroism (CD) imaging experiments. Then a homogeneous mixture is regenerated upon heating to 55 °C, as shown by CD imaging. Under self‐catalytic conditions, a homogeneous solution spontaneously changed to a heterogeneous solution in the process of hetero‐double‐helix formation.