アイテム詳細

要旨

ESR, ENDOR and triple resonance studies of 1,4-dihydro-1,3-diphenyl- (1a) and 3-tert-butyl-1,4-dihydro-1-phenyl-1,2,4-benzotriazinyl (2a) and of the corresponding radical cation 3a (2a protonated at N-4) yielded the magnitude and the sign of almost all of the 1H and 14N hyperfine coupling (HFC) constants. Their assignment was performed using various 2H labelled and/or methyl substituted derivatives. Both radical groups show major hyperfine coupling to the three 14N nuclei. In the uncharged species 1a and 2a, the spin density at N-4 apparently directs the 1H HFC pattern in the 1,2,4-benzotriazinyl component, a(H-5) and a(H-7) being larger than a(H-6) and a(H-8). In the radical cation, on the other hand, N-1, with an unusually large splitting of 9.9 G, is the position of highest spin density which determines the 1H HFC pattern, a(H-6) and a(H-8) being larger than a(H-7).