141. The Vitamin-B12-derived Co(III)-Complex 'Pyrocobester' as Photosensitizer and as Substrate in Reactions Involving 'Singlet Oxygen'

Article abstract of DOI:10.1002/hlca.19830660517

The vitamin-B₁₂ derivative 'pyrocobester'(1) acts as photosensitizer in its light-induced oxygenation which involves 'singlet oxygen' (¹O2) and which gives '5,6-dioxosecopyrocobester' (2) cleanly.The identity of the photosensitizer is deduced from a match of the 'photochemical action spectrum' of the photooxygenation with the UV/VIS absorption spectrum of 1.The involvement of ¹O2 in this reaction is established on the basis of solvent and solvent H/D isotope effects, of quenching studies with β-carotene and of competition experiments with 9,10-dimethyl-anthracene.Also, decomposition of the thermal ¹O2-source 1,4-dimethylnaphthalene-1,4-endoperoxide in a solution of 1 induces a clean oxygenation of 1 to2 in the dark as well.