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Selective Encapsulation of Chloride Ions within Novel Cage Host Complexes in the Presence of Equimolar Amounts of Chloride and Bromide Ions
Author(s) -
Ichikawa Kazuhiko,
Izumi Mitunori,
Goto Daiju,
Ito Naohito
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(20011203)7:23<5094::aid-chem5094>3.0.co;2-f
Subject(s) - chemistry , chloride , bromide , halide , ion , methylene , solvation , iodide , inorganic chemistry , host–guest chemistry , intramolecular force , supramolecular chemistry , molecule , medicinal chemistry , stereochemistry , organic chemistry
Four macrotricyclic cage hosts which feature four positive binding sites oriented toward the center of the intramolecular cavity are presented as promising candidates for anion receptors and they have been expected to play a important role in the selective encapsulation of the halide ion Cl − or Br − . The complementarity between a macrotricyclic quaternary ammonium ion and Cl − was achieved by fine‐tuning of the four ammonium nitrogen atoms and the endocyclic methylene groups. The cage hosts [R 4 N 4 (C 5 H 10 ) 4 (C 6 H 12 ) 2 ] 4+ (abbreviated as [556]) showed perfect encapsulation of all chloride ions in acetonitrile at 0< r =([Cl − ] o /[[556]] o )≤1 within the sensitivity of the 1 H NMR spectra in combination with a rather slow chemical exchange of the Cl − ion in an encapsulation/decapsulation equilibrium with [556]. Further, the selective encapsulation of all the chloride ions into [556] cage occurs unambiguously at r =1 in the presence of equimolar amounts of Br − . The structural complementarity of the newly designed [556] host prevails over the Hofmeister‐series restraints determined by differences in Gibbs free energy of halide anion solvation.