Hydrazine Cation Radical Formation in γ-Irradiated Single Crystals of Hydrazinium Hydrogen Oxalate

Room-temperature γ irradiation of hydrazinium hydrogen oxalate single crystals yields the hydrazine positive ion, which has been studied by electron spin resonance. The complex is planar, symmetry D2h, with the unpaired electron delocalized over the two nitrogen nuclei, which have the axial hyperfine coupling tensor AN = (2.5, 2.5, 27.6)G, aN = 11.0 G. The principal components of the proton coupling tensors are AH = (+2, −20.6, −13.0)G, aH = −10.4 G. The relative signs of the latter principal elements have been ascertained by comparing experimental and calculated spectra, for orientations of the crystal where ΔMI = 1 transitions are observed. The radical has a different orientation in the crystal compared with that of the parent ion. The reorientation is thought to be due to the influence of the hydrogen bonds between the hydrazine positive ions and neighboring oxygen atoms.