A fluorescent host-guest complex of cucurbituril in ...
|Title||A fluorescent host-guest complex of cucurbituril in solution: a molecular Jack O'Lantern|
|Author(s)||B. Wagner, S. Fitzpatrick, M. Gill, A. MacRae, N. Stojanovic|
|Journal||Canadian Journal of Chemistry / Revue Canadienne De Chimie|
|Abstract||Fluorescence enhancement of a probe molecule in solution by the container molecule cucurbituril (CB) is reported for the first time. The fluorescence of the probe 2-anilinonaphthalene-6-sulfonate (2,6-ANS) in aqueous Na2SO4 solution is found to increase by a maximum factor of 5.0 upon addition of cucurbituril. This fluorescence enhancement is the result of the formation of a host-guest inclusion complex, in which the guest 2,6-ANS is incorporated inside the cavity of the host, cucurbituril. Measurement of the enhancement as a function of cucurbituril concentration yielded a value of the equilibrium constant (K) of 52 +/- 10 M-1. It is proposed that the mode of inclusion involves the phenyl group of the 2,6-ANS, because of the relatively small size of the cucurbituril cavity. It is further proposed that the observed enhancement is a result of loss of rotational mobility of the phenyl ring relative to the naphthyl fluorophore of 2,6-ANS upon inclusion of the phenyl ring, Since the name cucurbituril is derived from the Latin word for "pumpkin," this fluorescent host-guest complex is referred to as a "molecular Jack O'Lantern," with the 2,6-ANS serving as the candle.|
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