CIDNP in the Photolysis of Coenzyme B 12 Model Compounds Suggesting That C−Co Bond Homolysis Occurs from the Singlet State

1H CIDNP has been observed following the photolysis of two coenzyme B12 model compounds, ethyl[N,N‘-ethylenebis(salicylideneaminato)]cobalt(III) and benzylaquocobaloxime. Polarization of the alkyl groups attached through a carbon atom to the cobalt(III) metal center has been observed and is consistent with photohomolysis of the C−Co bond to generate a singlet radical pair. The analysis of CIDNP effects clarifies the apparent contradiction between the CIDEP and magnetic field effect studies reported previously.