Anisotropic Electron Spin Resonance Spectrum of PF2 in Low‐Temperature Matrices

Abstract

The anisotropic electron spin resonance spectrum of the PF2 radical has been observed. P2F2 was thermally decomposed by passing the gas over a hot wire. The radicals produced were trapped in an argon matrix on a flat sapphire rod held at 20°K. The same radicals were formed by photolysis of PF2H in an argon matrix. In contrast to N2F4, PF2 radicals were not detected unless the P2F4 was heated above 200°C. The observed 12‐line ESR spectrum is interpreted as being due to randomly oriented nonrotating radicals with axially symmetric gg and hyperfine tensors. Based on computer‐simulated spectra, the following assignment has been made: g‖ = 2.0011,g⊥ = 1.9922;C‖ = (P) = 307G,C⊥(P) = − 83.0G;C‖(F) = 127G,C⊥(F) = 33.5Gg‖=2.0011,g⊥=1.9922;C‖=(P)=307G,C⊥(P)=−83.0G;C‖(F)=127G,C⊥(F)=33.5G. The same radical was also trapped in different matrices. The nature of the trapping sites and the effect of environment on the radicals is discussed. Comparison with data available for NF2 indicates that the unpaired electron in PF2 is localized on the central atom to a greater extent than it is in NF2. Extended Hückel calculations also give this result.