The host-guest chemistry of proflavine with cucurbit[6,7,8]urils

Kemp, Sharon and Wheate, Nial J. and Stootman, Frank H. and Aldrich-Wright, Janice R. (2007) The host-guest chemistry of proflavine with cucurbit[6,7,8]urils. Supramolecular Chemistry, 19 (7). pp. 475-484. ISSN 1061-0278 (http://dx.doi.org/10.1080/10610270601124019)

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Abstract

The binding of the polyaromatic guest, 3,6-diaminoacridine (Proflavine) to cucurbit[n]uril (CB[n]) where n = 6, 7 and 8 has been studied by fluorescence spectrophotometry and binding constants determined using a least squares fitting method. Titration of CB[8] into a solution of Proflavine results in a 95% decrease in fluorescence up to a CB[8] to Proflavine ratio of 2:1. From the induced fluorescence spectra a binding constant of 1.9 times 107 M- 1 was determined. When Proflavine is titrated into a solution of CB[8] a similar binding constant is calculated (1.3 times 107 M- 1). Titration of CB[6] into a solution of Proflavine yields a decrease in fluorescence of 18-20%, but no binding is observed beyond what is seen within experimental error. Finally, titration of CB[7] into a solution of Proflavine results in an increase in fluorescence (32%) and a blue-shift of the emission wavelength from 509 nm to 485 nm. From the induced fluorescence spectra a binding constant of 1.65 times 107 M- 1 was determined. From 1H NMR it appears that the decrease in fluorescence for Proflavine with CB[6] and CB[8] is due to collisional quenching, whereas the increase in fluorescence with CB[7] may be due to rotational restriction.

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