Far infrared magnetic resonance in FeSiF6⋅6H2O and Fe(SPh)42−

Abstract
The technique of far infrared magnetic resonance is used to investigate the zero‐field splittings of the spin quintet associated with the lowest orbital state of high‐spin ferrous iron. Two examples are discussed in detail: the ’’axial’’ compound, ferrous fluosilicate, and the ’’rhombic’’ compound, tetrakis thiophenolate Fe(II). The data are analyzed within the context of the spin Hamiltonian, and values of D and E are directly obtained from the spectra using a closed form solution of the eigenvalue problem. The application of this technique to the high‐spin ferrous forms of biomolecules such as the heme and iron‐sulfur proteins is also discussed.