Why, on interaction of urea-based receptors with fluoride, beautiful colors develop.
[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.
Dipartimento di Chimica Generale, Università di Pavia, viale Taramelli 12, 27100 Pavia, Italy.
David
D
Esteban-Gómez
Luigi
L
Fabbrizzi
Maurizio
M
Licchelli
D000085:Acetates / Q000737:chemistry; D000838:Anions; D003116:Color; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004347:Drug Interactions; D004583:Electrons; D005459:Fluorides / Q000737:chemistry*; D006860:Hydrogen Bonding; D006878:Hydroxides / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D011522:Protons; D014508:Urea / Q000737:chemistry*
D000085:Acetates; D000838:Anions; D006878:Hydroxides; D010710:Phosphates; D011522:Protons; D014508:Urea; D005459:Fluorides; D004121:Dimethyl Sulfoxide