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Slippage of a porphyrin macrocycle over threads of varying bulkiness: implications for the mechanism of threading polymers through a macrocyclic ring.

Authors :
Deutman AB
Varghese S
Moalin M
Elemans JA
Rowan AE
Nolte RJ
Source :
Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2015 Jan 02; Vol. 21 (1), pp. 360-70. Date of Electronic Publication: 2014 Oct 24.
Publication Year :
2015

Abstract

Threading of a polymer through a macrocyclic ring may occur directly, that is, by finding the end of the polymer chain, or by a process in which the polymer chain first folds and then threads through the macrocyclic ring in a hairpin-like conformation. We present kinetic and thermodynamic studies on the threading of a macrocyclic porphyrin receptor (H2 1) onto molecular threads that are blocked on one side and are open on the other side. The open side is modified by groups that vary in ease of folding and in bulkiness. Additionally, the threads contain a viologen binding site for the macrocyclic receptor, which is located close to the blocking group. The rates of threading of H2 1 were measured under various conditions, by recording as a function of time the quenching of the fluorescence of the porphyrin, which occurs when receptor H2 1 reaches the viologen binding site. The kinetic data suggest that threading is impossible if the receptor encounters an open side that is sterically encumbered in a similar way as a folded polymer chain. This indicates that threading of polymers through macrocyclic compounds through a folded chain mechanism is unlikely.<br /> (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Details

Language :
English
ISSN :
1521-3765
Volume :
21
Issue :
1
Database :
MEDLINE
Journal :
Chemistry (Weinheim an der Bergstrasse, Germany)
Publication Type :
Academic Journal
Accession number :
25345395
Full Text :
https://doi.org/10.1002/chem.201403740