E.S.R. and ENDOR studies of X-irradiated 1-phenyl-3-thiosemicarbazide single crystals

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Abstract
By means of E.S.R. and ENDOR spectroscopy, a radical identified as C5H6NNHCSNH2 has been studied in X-irradiated single crystals of 1-phenyl-3-thiosemicarbazide, C6H5NHNHCSNH2. The unpaired electron interacts with one nitrogen and three hydrogen nuclei. The nitrogen interaction, studied with E.S.R., has the principal values A 1=76·2±8 MHz; A 2=10·0±8 MHz; A 3=0·0±8 MHz, and is characteristic of a π-type radical with 50 per cent of the spin density localized in a nitrogen 2p orbital. The three hydrogen interactions, studied with ENDOR, have the principal values These interactions are of the CH α-type and arise from hydrogen atoms on the phenyl ring. The remaining spin density is distributed on the phenyl ring with virtually the same amount in each of the three different carbon 2pπ orbitals.