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Cooperativity in the Folding of Helical m ‐Phenylene Ethynylene Oligomers Based upon the `Sergeants‐and‐Soldiers' Principle
Author(s) -
Prince Ryan B.,
Moore Jeffrey S.,
Brunsveld Luc,
Meijer E. W.
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011001)7:19<4150::aid-chem4150>3.0.co;2-f
Subject(s) - side chain , circular dichroism , folding (dsp implementation) , oligomer , phenylene , chemistry , crystallography , twist , acetonitrile , stereochemistry , polymer chemistry , polymer , organic chemistry , mathematics , electrical engineering , engineering , geometry
The `Sergeants‐and‐Soldiers' principle has been examined in a series of m ‐phenylene ethynylene oligomers containing both chiral and achiral side chains. Circular dichroism (CD) spectroscopy was used to examine the twist sense bias of the helical conformation in the polar solvent acetonitrile. A nonlinear dependence of the CD signal on the amount of chiral side chains was observed revealing cooperative interactions among the side chains through the backbone. On the other hand, the experiments indicate that in acetonitrile a full bias of the helicity cannot be accomplished by chiral side chains alone. Nevertheless, the folded oligomers are highly ordered since the placement of a single chiral side chain at the beginning of an oligomer results in the induction of a strong twist sense bias into the ordered helical conformation.