METAL-ION COMPLEXATION BY THE PHOSPHORYL AND THE CARBONYL GROUPS PROBED BY O-17 NMR-SPECTROSCOPY

Interactions between compounds containing phosphoryl, carbonyl, or hydroxyl groups (or combinations of these groups) with metal ions (Na+, Mg2+)were probed in CD3CN solutions by O-17 NMR spectroscopy, For all phosphoryl and carbonyl substrates a strong high-field shift of the P=O and C=O signals was observed on the addition of a salt; no shift was observed, however, for the OH group signal, indicating that no chelation takes place in the hydroxyphosphoryl (or hydroxycarbonyl) derivatives. For 2-hydroxy-3-benzoylpropylphosphonic diester the O-17 NMR studies, together with conformational analysis based on the H-1 spectroscopy, demonstrated the chelation of a metal ion by the P=O and C=O functions (formation of an eight-membered cyclic structure) with the OH group involved in the intramolecular hydrogen bonding, but not in the complexation to the metal ion.