Abstract
The 1:1 and 2:1 host–guest complexation of a series of 1,n-bis(isoquinolinium)alkane dications (Iq(CH2)nIq2+, n = 2, 4, 5, 6, 8, 9, 10 and 12, and Iq(p-xylene)Iq2+) by cucurbit[7]uril (CB[7]) in aqueous solution has been investigated by 1H NMR spectroscopy and ESI mass spectrometry. The site of binding of the first CB[7] is dependent on the nature of the central linker group, with encapsulation of the p-xylene group or the polymethylene chain when n = 6–10.With shorter (n = 2–5) or longer (n = 12) chains, the first CB[7] binds over an isoquinolinium group. With a second CB[7], the binding of the central group is abandoned in favour of the CB[7] hosts encapsulating the two cationic isoquinolinium termini. The 1:1 and 2:1 host–guest stability constants are related to modes of binding and the nature of the central linkers, and are compared with dicationic guests bearing different terminal groups.
Acknowledgements
The authors acknowledge the financial support by the Natural Sciences and Engineering Research Council of Canada and Queen's University for conducting this research.