Nature of electric field-gradient tensor in strong-field tetragonal and pseudo-tetragonal complexes of divalent iron
Mössbauer measurements made in the presence of large magnetic fields show that in phthalo-cyaninebis(pyridine)iron(II) the electric field-gradient at the iron nucleus is of positive sign. This indicates that the metal atom is bonded more strongly to the planar ligand than it is to the axial ligands. Similar measurements made on bis(1,2-cyclohexane-dioxime)bis(imidazole)iron(II) and bis(1,2-cyclohexanedioxime)bis(ammonia)-iron(II) show that in both these compounds the electric field-gradient tensor has a large asymmetric component. Possible reasons for this are discussed.