Electron Spin Resonance of High-Spin d5 Systems

The electron spin resonance spectra of polycrystalline samples of some sideramines (coprogen, ferrichrysin, ferricrocin, and ferrirubin), transferrin, and conalbumin are reported both at 9.3 and 36 kMc/sec and at various temperatures. These results have been interpreted in terms of a spin Hamiltonian of the form H = gβH·S + D[Sz2 − 13S(S + 1)] + E(Sx2 − Sy2). The application of this interpretation to other high-spin d5 systems both in single-crystal and polycrystalline form is discussed.