Determination of the purity of cucurbit[n]uril (n = 7, 8) host samples

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The formation of highly stable inclusion complexes in aqueous solution between the organometallic cobaltocenium cation (Cob +) and the hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) was used to develop a simple method, based on UV-vis titrations, to assay the purity of samples of these two hosts. The equilibrium association constant (K) of the Cob +@CB7 complex had been previously reported by our group as 5.7 × 10 9 M -1 at 25 °C in 50 mM sodium acetate medium. In this work, we determine a K value of 1.9 × 10 8 M -1 at 25 °C in the same medium for the Cob +@ CB8 complex. The high stability of these complexes and their decreased molar absorptivity coefficients (at 261 nm), compared to that for free Cob +, lead to straightforward titration plots when graphing absorbance versus concentration of added CB7 (or CB8) host, at constant Cob + concentration (Figure presented).

Original languageEnglish (US)
Pages (from-to)10275-10278
Number of pages4
JournalJournal of Organic Chemistry
Issue number24
StatePublished - Dec 16 2011

ASJC Scopus subject areas

  • Organic Chemistry


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