Anion receptors containing -NH binding sites: hydrogen-bond formation or neat proton transfer?
When the amide-containing receptor 1(+) is in a solution of dimethyl sulfoxide (DMSO) in the presence of basic anions (CH(3)COO(-), F(-), H(2)PO(4) (-)), it undergoes deprotonation of the -NH fragment to give the corresponding zwitterion, which can be isolated as a crystalline solid. In the presence of less basic anions (Cl(-), Br(-), NO(3) (-)), 1(+) establishes true hydrogen-bond interactions of decreasing intensity. The less acidic receptor 2(+) undergoes neat proton transfer with only the more basic anions CH(3)COO(-) and F(-), and establishes hydrogen-bond interactions with H(2)PO(4) (-). An empirical criterion for discerning neutralisation and hydrogen bonding, based on UV/Vis and (1)H NMR spectra, is proposed.
Amendola
Valeria
V
Dipartimento di Chimica Generale, Università di Pavia viale Taramelli 12, 27100 Pavia, Italy.
Boiocchi
Massimo
M
Fabbrizzi
Luigi
L
Palchetti
Arianna
A
D000588:Amines / Q000737:chemistry*; D000838:Anions; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D011955:Receptors, Drug / Q000737:chemistry*; D013053:Spectrophotometry
D000588:Amines; D000838:Anions; D011955:Receptors, Drug