Issue 8, 2004

Threading/dethreading processes in pseudorotaxanes. A thermodynamic and kinetic study

Abstract

Pseudorotaxanes are host–guest complexes made of a thread-like component penetrating a bead-like component. We have investigated, by a stopped-flow technique, the threading/dethreading kinetics of pseudorotaxanes formed between a tetracationic cyclophane, cyclobis(paraquat-p-phenylene), and thread-like compounds consisting of a naphthalene ring system with appended –(OCH2CH2)nOH groups (n from 0 to 3) on the 1 and 5 positions. The association and rate constants have been measured in MeCN (from 276 to 293 K) and H2O (from 276 to 313 K). In MeCN solution, the association constant increases with increasing length of the appended chain (e.g., Kass = 1.0 × 103 M−1 for n = 0 and Kass = 4.0 × 104 M−1 for n = 3, at 293 K); in H2O, the association constants are larger than in MeCN, but almost independent of the chain length. Both the threading (kt) and dethreading (kd) rate constants are larger in MeCN than in H2O and decrease with increasing chain length (e.g., kt > 108 and kt = 4 × 106 M−1 s−1 for n = 0 and n = 3, respectively, in H2O at 276 K). Thermodynamic and kinetic parameters have been obtained and the role played by the length of the chains appended to the naphthalene ring system is discussed.

Graphical abstract: Threading/dethreading processes in pseudorotaxanes. A thermodynamic and kinetic study

Article information

Article type
Paper
Submitted
05 Dec 2003
Accepted
05 Apr 2004
First published
15 Jul 2004

New J. Chem., 2004,28, 1032-1037

Threading/dethreading processes in pseudorotaxanes. A thermodynamic and kinetic study

M. Venturi, S. Dumas, V. Balzani, J. Cao and J. F. Stoddart, New J. Chem., 2004, 28, 1032 DOI: 10.1039/B315933G

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