Structure-reactivity relationship in interlocked molecular compounds and in their supramolecular model complexes

Masumi Asakawa, Christopher L. Brown, Stephan Menzer, Françisco M. Raymo, J. Fraser Stoddart, David J. Williams

Research output: Contribution to journalArticle

42 Scopus citations

Abstract

Examination of the pseudorotaxane-like geometries adopted in the solid state by a series of 1:1 complexes revealed significant differences in the hydrogen bonding interactions between oxygen atoms in some hydroquinone-based guests carrying polyether/polyester functions and the acidic hydrogen atoms on the bipyridinium units of the host-cyclobis(paraquat-p-phenylene). These differences are reflected directly in the stabilities of the complexes in solution and dramatic changes in the magnitudes of their association constants (K(a) values ranging from 130 to 4300 M-1 in MeCN at 25 °C) are observed upon varying the location of the carbonyl ester function(s) along the polyether/ester chains. A similar effect (K(a) values ranging from 5 to 730 M-1 in Me2CO at 25 °C) was observed in the binding of paraquat as its bipyridinium bis(hexafluorophosphate) salt by analogous macrocyclic hydroquinone-based mono- and bis-lactones. Investigations of the kinetics of hydrolyses of the ester functions revealed that-while inert in their free forms-the macrocyclic mono- and bis-lactones undergo hydrolysis when incorporated within catenanes composed of one of these macrocyclic lactones and cyclobis(paraquat-p-phenylene). Presumably, the enhanced reactivity of the ester functions is a result of [C-H...O] hydrogen bonding interactions involving the ester carbonyl oxygen atoms and the acidic hydrogen atoms on the bipyridinium units, as suggested by single-crystal X-ray crystallographic analyses. Thus, cyclobis(paraquat-p-phenylene) can act as a mechanically-interlocked 'catalyst'.

Original languageEnglish (US)
Pages (from-to)2614-2627
Number of pages14
JournalJournal of the American Chemical Society
Volume119
Issue number11
DOIs
StatePublished - Mar 19 1997
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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