14N NMR studies of free radicals: Application to α,α-diphenyl-β-picrylhydrazyl (DPPH)

Abstract

Using NMR, we establish that the 14 N hyperfine coupling, A N , of the -NO 2 groups in DPPH is −0.42 ± 0.05 G. This must correspond to the smallest splitting observed in the high-resolution EPR spectra of DPPH. We find that for such small 14 N splittings in free radicals, the NMR method has distinct advantages over ELDOR, ENDOR, and tripleresonance techniques.