Paramagnetic Resonance of Fe3+ in Polycrystalline Ferrichrome A

Abstract

Polycrystalline samples of iron-containing ferrichrome A, a cyclic hexapeptide obtained from the fungus Ustillago sphaerogena, have been investigated by paramagnetic resonance. Spectra were obtained at several temperatures between 300° and 1°K; a prominent line of 400-Oe width located at g=4.3 was observed at all temperatures, while at 1°K additional resonances at g values of 9.6, 1.3, and 1.0 were observed. The spectra are interpreted by assuming a spin Hamiltonian containing crystal-field terms large compared with the Zeeman splittings; the crystal-field situation is intermediate between the case of axial symmetry, with H=D[Sz2−(1/3)S(S+1)]+gβS·H and a model proposed by Castner, Newell, Holton, and Slichter to explain certain iron resonances occurring at g=4.3, with H=E(Sx2−Sy2)+gβS·H. We have computed g values, energy eigenvalues, and eigenfunctions to be expected for the region between these two extremes, and the results should be useful in interpreting similar spectra due to iron situated in strong crystal fields of low symmetry.

Alternative zero-field splitting (ZFS) parameter sets and standardization for Mn2+ ions in various hosts exhibiting orthorhombic site symmetry

“…recognized and discussed [45]. The number of applications of the standardization idea [6][7][8][9][10] has been growing since its comprehensive extensions appeared [20,21]; see the recent papers [22][23][24] and references therein.…”

“…Instances of the CF=ZFS confusion are evident in several phrases in [60], e. Both systems exhibit monoclinic space group symmetry and thus a suitably modified CAS*, i.e. with one crystallographic axes (usually the c-axis) taken as perpendicular to the remaining two axes, should be adopted A c c e p t e d m a n u s c r i p t 7 instead of CAS (a, b, c), which does not form a Cartesian axis system [56]. No modified CAS* has been defined in [60,61].…”

“…The latter Hamiltonian is often confused in EMR literature with the crystal-field (CF) Hamiltonian, in spite of their physically different nature [5]. The standardization idea has originally been introduced in EMR area for the second-rank conventional ZFS terms based on the observation that the ratio of the orthorhombic (E) to axial (D) ZFS parameters (ZFSPs): λ = E/D can always be limited to the range (0, ± 1/3) by appropriate choice of coordinate system [6,7,8].…”

Electron spin resonance and distribution of some elements in shales

“…A similar reso nance was recognized in some clays and clay minerals (HALL et al, 1974;MEADS and MALDEN, 1975;ANGEL and VINCENT, 1978), micas (KEMP, 1971(KEMP, , 1972 and organic materials containing Fe(III) (WICKMAN et al, 1965;CHESHIRE et al ., 1977;SENESI et al, 1977).…”

Design of novel iron compounds as potential therapeutic agents against tuberculosis

“…For Fe-L1, Fe-L2, and Fe-L4, a weak resonance around 80 mT (g eff~9 ) was observed. These EPR signals are characteristic of magnetically isolated high-spin Fe(III) in a rhombic environment [30,31] and arise from transitions between m S = ±1/2 (g eff~9 ) or m S = 3/2 (g eff~4 .3) states.…”