Abstract
Exposure of methylcobalamin in CD3OD–D2O glasses at 77 K to a high-pressure mercury arc gave low yields of methyl and CD2OD radicals and high yields of a radical-CoII pair species (triplet state), which on annealing was converted into normal CoIIB12r. The mean separation between cobalt and the radical was ca. 8.3 A. The ethyl derivative gave broad features for CoIIB12r and alkyl radicals, suggesting weak spin–spin interaction and hence greater mean separation. In contrast, the acetyl derivatives gave no detectable features at 77 K, but intense CoIIB12r features grew in on annealing above 77 K. We suggest that close random pair-trapping broadened all features beyond the detection limit at 77 K.For the coenzyme, in agreement with Lowe et al., no detectable reaction occurred on photolysis at 77 K, but normal photolysis was detected above ca. 200 K. Again, some random pair-trapping was evident.
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Schedule a callMore From: Journal of the Chemical Society, Perkin Transactions 2
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