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Anion Receptors Containing ‐NH Binding Sites: Hydrogen‐Bond Formation or Neat Proton Transfer?
Author(s) -
Amendola Valeria,
Boiocchi Massimo,
Fabbrizzi Luigi,
Palchetti Arianna
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400592
Subject(s) - deprotonation , chemistry , hydrogen bond , zwitterion , proton , amide , ion , dimethyl sulfoxide , medicinal chemistry , crystallography , inorganic chemistry , stereochemistry , molecule , organic chemistry , physics , quantum mechanics
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.