The Mechanisms Of Oxidation Of Nadh Analogs .3. Stimulated Nuclear-Polarization (Snp) And Chemically-Induced Dynamic Nuclear-Polarization (Cidnp) In Low Magnetic-Fields In Photooxidation Reactions Of 1,4-Dihydropyridines With Quinones

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.