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.

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Electron spin resonance spectra are reported for the complexes MnL,X, (L = dipyridylamine or o-phenanthroline, X = CI, Br, I, or NCS; L = biuret, X = CI, Br, or I). Distortion parameters D and ' h are deduced by comparison of the observed spectra with calculated transitions. Electronic and low-energy vibrational spectra of the compounds are also reported. tories, Imperial College, London S.W.7COMPLEXES of manganese@) can give rise 1 to e.s.r. regular geometry of this type, distortions again tending spectra which reflect their stereochemistry. In particu-to increase A. However, for a &-arrangement, the lar, studies have been made of systems with unidentate value of D is expected to be appreciably smaller than ligands having pseudo-octahedral2 (Dh) and pseudo-for a trarts-geometry with the same ligands.