Selective measurements of heteronuclear overhauser effects: Structural applications

A NMR method for determining internuclear distances between dipolarly coupled nuclei is here proposed. As a model system, salicylaldehyde has been investigated. A selective presaturation of C1H and O2′ H protons yields Overhauser effects on C1, C1′ and C2′ resonances. From a combined use of these Overhauser effects and13C spin-lattice relaxation rates, internuclear distances between irradiated protons and carbon nuclei dipolarly coupled to them can be calculated. Furthermore, the obtained selective Overhauser effects can simultaneously evidentiate donor and acceptor moieties of hydrogen bonds, as in the present study in which the hydrogen bonding between the C1 carbonyl and the O2′ H proton was clearly delineated. © 1984 Societá Italiana di Fisica.