Cucurbituril metal ions

Kim, Kimoon, Self-Assembly of Interlocked Structures with Cucurbituril Metal Ions and Metal Complexes, 5, 371. 

The presence in dyehouse effluents of typical dye-complexing metal ions is an environmentally sensitive issue, such metallic contamination arising mostly from the decomposition of metal-complex dyes [26]. The synthetic complexing agent cucurbituril (section 10.3.2) can be used to selectively extract such metal ions from the effluent. 

D. Whang, J. Heo, J.H. Park, K. Kim, A Molecular Bowl with Metal Ion as Bottom Reversible Inclusion of Organic Molecules in Cesium Ion Complexed Cucurbituril , Angew. Chem. Int. Ed., 37,78 (1998)... 

Some of our recent work on the construction of interlocked structures is described in this short review. In the design of these structures, the barrel-shaped molecule cucurbituril is used as a molecular bead and metal ions or metal complexes are used as glue or angle connectors . The examples given here demonstrate the efficiency and control in the self assembly of highly organized supramolecular species. 

Metal ion binding phenomenon of cucurbituril was mentioned even in the original report of cucurbituril by Behrend et al. [13] Buschmaim et al. recently studied complexation of alkaline metal ions to cucurbituril by UV-vis spectroscopy (a) Buschmann, H.-J., Cleve, E, A. Schollmeyer, E. Inorg. Chim. Acta 1992,193, 93, (b) Hoffmann, R., Knoche, W., Fenn, C. and Buschmann, H.-J. J. Chem. Soc. Faraday Trans., 1994, 90, 1507. The complex formation constants were measured in the presence of metal salts in the range of 1 X 10 -5 X 10 M. 

The first cucurbituril derivative decamethylcucurbit[5]uril (Me-CB[5]) (Chart I) was synthesized from dimethylgly-coluril and formaldehyde in 1992. " The X-ray structural analysis shows a cavity of 4 A in diameter and two identical portals of 2.5 A in diameter. Bradshaw and coworkers studied complexation of Me-CB[5] with metal ions in 50% formic acid/water solution by calorimetric and potentiometric methods.Me-CB[5] binds most metal ions in a 1 1 stoichiometry in the acidic solution. Interestingly, Me-CB[5] shows exceptionally high affinity for Pb ion (log K > 9). which is mainly due to the size match between Pb and Me-CB[5] portals. The p a value (9.56) for protonation of Me-CB[5] indicates that Me-CB [5] behaves as a base in an aqueous solution. 

Whang D, Heo J, Park JH, Kim K. A molecular bowl with metal ion as bottom reversible inclusion of organic molecules in cesium ion complexed cucurbituril. Angew Chem Int Ed... 

Hoffmann R, Knocke W, Fenn C. Host-guest complexes of cucurbituril with the 4-methylbenzylammonium ion, alkali-metal cations and NH4. J Chem Soc Earaday Trans 1994 90 1507-11. 

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