title: Anion-induced urea deprotonation.
abstract: The urea-based receptor 1 (1-(7-nitrobenzo[1,2,5]oxadiazol-4-yl)-3-(4-nitrophenyl)urea, L--H), interacts with X- ions in MeCN, according to two consecutive steps: 1) formation of a hydrogen-bond complex [L--H...X]-; 2) deprotonation of L--H to give L- and [HX2]-, as shown by spectrophotometric and 1H NMR titration experiments. Step 2) takes place with more basic anions (fluoride, carboxylates, dihydrogenphosphate), while less basic anions (Cl-, NO2-, NO3-) do not induce proton transfer. On crystallisation from a solution containing L--H and excess Bu4NF, the tetrabutylammonium salt of the deprotonated urea derivative (Bu4N[L]) was isolated and its crystal and molecular structure determined.
authors.affiliation: Centro Grandi Strumenti, Università di Pavia via Bassi 21, 27100 Pavia, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Boiocchi
authors.forename: Laura
authors.initials: L
authors.lastname: Del Boca
authors.forename: David
authors.initials: D
authors.lastname: Esteban-Gómez
authors.forename: Luigi
authors.initials: L
authors.lastname: Fabbrizzi
authors.forename: Maurizio
authors.initials: M
authors.lastname: Licchelli
authors.forename: Enrico
authors.initials: E
authors.lastname: Monzani