Abstract
The CIDNP enhancement induced in a weakly coupled magnetic nucleus, N w , can be suppressed in the presence of a strongly coupled nucleus, N 5 . This effect was observed at high fields (58.3 kG) for both biradicals and radical pairs, irrespective of whether the two magnetic nuclei belong to the same radical or to different radicals. The observed effects can be rationalized on the basis of the exact radical-pair theory. This is the first report of such phenomena. © 1991 American Chemical Society.