Electron paramagnetic resonance spectra of the ·O 2F radical in liquid and solid O 2F 2

Abstract

It has been established that the paramagnetism of O 2F 2 is due to the ·O 2F radical. The electron paramagnetic resonance spectrum of liquid dioxygen difluoride (O 2F 2) contains an isotropic doublet as a result of a hyperfine interaction with one fluorine nucleus. The doublet has a splitting of 15.9 gauss, and is centered at a g-value of 2.0033. Liquid O 2F 2 prepared with oxygen enriched to 51.2% with 17O exhibited a complex isotropic spectral pattern also centered at g = 2.0033 with hyperfine interactions of 15.9 gauss from a fluorine nucleus and 22.4 gauss and 14.9 gauss from two nonequivalent oxygen nuclei. The observed pattern is a result of four spectra superimposed one upon the other. The following isotopic species contributed to the paramagnetism: ·OOF, 24.4% abundant; · 17OOF, 24.4%; ·O 17OF, 24.4%; and · 17O 17OF, 26.8%. The EPR spectrum of solid O 2F 2 and solid 17O 2F 2 consisted of an anisotropic powder pattern characteristic of axial symmetry. The values of the fluorine hyperfine interaction observed were A ⊥ = −24.0 gauss, and A ∥ = 98.8 gauss. The average g-value was 2.0033. The values of the hyperfine interactions were used to calculate the unpaired electron density in various orbitals. The unpaired electron density in the radical was high in the 2 p orbitals of the oxygen atoms and low in orbitals of the fluorine atom.