Supramolecular chemistry of p-sulfonatocalix[5] arene: A water-soluble, bowl-shaped host with a large molecular cavity
- King`s College London (United Kingdom)
- Univ. of Missouri, Columbia, MO (United States)
- Los Alamos National Lab., NM (United States)
The first X-ray crystallographic studies are reported for water-soluble inclusion complexes of the macrocyclic p-sulfonatocalix[5]arene (1b). The complexes Na{sub 7} [p-sulfonatocalix[5]arene].18H{sub 2}O (2) and Na{sub 5} [p-sulfonatocalix]5[arene].py-N-O.8.5H{sub 2}O (3) containing water and pyridine N-oxide (py-N-O) guest species have been isolated. In 2 the large bowl-shaped cavity of the host molecule is occupied by a total of three water molecules, while for 3 a single molecule of pyridine N-oxide is included and interacts with the host via a strong hydrogen bond to a protonated sulfonate substituent. The behavior of 1b as a ligand for a number of lanthanide elements is also reported. Low temperature X-ray structural studies reveal that coordination of the Ln{sup 3+} metal ions to the calixarene ligand occurs exclusively via the sulfonato functionalities and not the phenolic oxygen atoms as suggested by Shinkai et al. for the complexation of UO{sub 2}{sup 2+} by lb. In complex 2 the calixarene exists as the heptaanion. In contrast, crystallization from acidic solution results in complexes 3-8 retaining all their phenolic protons. The protonation constants of 1b have been measured in aqueous solution: pK{sub a} = 10.96(8), 7. 63(5), and 4.31(1) at 25{degree}C and 0.1 M KNO{sub 3}. 24 refs., 8 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 159697
- Journal Information:
- Journal of the American Chemical Society, Vol. 117, Issue 46; Other Information: PBD: 22 Nov 1995
- Country of Publication:
- United States
- Language:
- English
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