Cooperativity in the folding of helical m-phenylene ethynylene oligomers based upon the 'Sergeants-and-Soldiers' principle

Citation
Rb. Prince et al., Cooperativity in the folding of helical m-phenylene ethynylene oligomers based upon the 'Sergeants-and-Soldiers' principle, CHEM-EUR J, 7(19), 2001, pp. 4150-4154
Citations number
24
Categorie Soggetti
Chemistry
Journal title
CHEMISTRY-A EUROPEAN JOURNAL
ISSN journal
09476539 → ACNP
Volume
7
Issue
19
Year of publication
2001
Pages
4150 - 4154
Database
ISI
SICI code
0947-6539(20011001)7:19<4150:CITFOH>2.0.ZU;2-U
Abstract
The 'Sergeants-and-Soldiers' principle has been examined in a series of m-p henylene ethynylene oligomers containing both chiral and achiral side chain s. Circular dichroism (CD) spectroscopy was used to examine the twist sense bias of the helical conformation in the polar solvent acetonitrile. A nonl inear dependence of the CD signal on the amount of chiral side chains was o bserved revealing cooperative interactions among the side chains through th e backbone. On the other hand, the experiments indicate that in acetonitril e a full bias of the helicity cannot be accomplished by chiral side chains alone. Nevertheless, the folded oligomers are highly ordered since the plac ement 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 con formation.