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Why, on interaction of urea-based receptors with fluoride, beautiful colors develop.

Esteban-Gómez D, Fabbrizzi L, Licchelli M

Dipartimento di Chimica Generale, Università di Pavia, viale Taramelli 12, 27100 Pavia, Italy.

[reaction: see text] Urea-based receptors, containing electron-withdrawing chromogenic substituents, in a DMSO solution, in the presence of varying excess of fluoride, do not form H-bond complexes, but undergo stepwise deprotonation of the two N-H fragments, an event which is signaled by the development of vivid colors. Double deprotonation is also observed in the presence of hydroxide. Less basic anions (CH3COO-, H2PO4-) induce deprotonation of only one N-H.

Published 1 July 2005 in J Org Chem, 70(14): 5717-20.
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