The Influence of Paramagnetic Species on the Inter-Nuclear Overhauser Effect

摘要

One of the greatest single factors responsible for the rapid growth of natural abundance 13C NMR spectroscopy is the deployment of selective and random noise proton 'decoupling'. However, proton decoupling is normally accompanied by an additional signal enhancement due to the operation of a 13C-1H Overhauser effect. It is shown that internuclear Overhauser enhancements can be substantially reduced if a paramagnetic species is added to the sample. Such reduction or elimination of the Overhauser enchancement can be accomplished without significant broadening of a nuclear resonance, if the nuclei observed are embedded within a molecule and those decoupled are in the periphery. In cases where Overhauser enhancements are not reduced to zero, the actual magnitude of the enhancement can be calculated from a plot of signal intensity versus concentration of paramagnetic species.