hide
Free keywords:
-
Abstract:
Radical particles formed during the photo-oxidation of 1,4-dihydropyridines (1,4-DHPs) by quinones in benzene and acetone have been characterized using stimulated nuclear polarization (SNP) and low-magnetic-field chemically induced dynamic nuclear polarization (CIDNP) techniques. The experimentally obtained hyperfine coupling constants of the 1,4-DHP radical ion and neutral radical qualitatively agree with those calculated using the INDO method. It has been found that the disproportionation reaction of two neutral nitrogen-centred 1,4-DHP radicals provides the main contribution to CIDNP in low magnetic fields.