Interplay of p-sulfonatocalix[4]arene and crown ethers en route to molecular capsules and "Russian dolls".
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 x 10(2)-9.9 x 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) approximately 3.1 x 10(3) M(-1).
Dalgarno
Scott J
SJ
School of Biomedical and Chemical Sciences, University of Western Australia, Crawley, Perth, WA 6909, Australia.
Fisher
Julie
J
Raston
Colin L
CL
D001665:Binding Sites; D047250:Calixarenes / Q000737:chemistry*; D043844:Crown Ethers / Q000737:chemistry*; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D010636:Phenols / Q000737:chemistry*
D043844:Crown Ethers; D010636:Phenols; C121325:calix(4)arene; D047250:Calixarenes