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Interplay of p ‐Sulfonatocalix[4]arene and Crown Ethers En Route to Molecular Capsules and “Russian Dolls”
Author(s) -
Dalgarno Scott J.,
Fisher Julie,
Raston Colin L.
Publication year - 2006
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/chem.200500968
Subject(s) - chemistry , aqueous solution , crown ether , ether , crystallography , lanthanide , phase (matter) , nuclear magnetic resonance spectroscopy , stability constants of complexes , aqueous two phase system , metal , stereochemistry , ion , organic chemistry
Abstract Diffusion‐ordered 1 H NMR spectroscopy techniques have been used to determine the binding strength of p ‐sulfonatocalix[4]arene (SO 3 [4]) towards a number of charged crown ether species in aqueous conditions. For several (doubly) charged (di)azacrown ethers, all were bound by SO 3 [4] either well or very well with binding constants between 5.1×10 2 –9.9×10 5 M −1 . These results correlate with, and thus explain the phenomenon of rapid capture of azacrown ethers in molecular capsules based on p ‐sulfonatocalix[4]arene and lanthanide metals. Similarly, the formation of “Russian doll” superanions in the solution phase is also elucidated. These superanions have been shown to selectively crystallise particular polynuclear aquated metal ions from mixtures in the aqueous phase. Neutral [18]crown‐6 is not bound by p ‐sulfonatocalix[4]arene and displays a binding constant of 0 M −1 . When sodium [18]crown‐6 is examined in a similar fashion, binding by SO 3 [4] is observed in solution with K a ∼3.1×10 3 M −1 .