Fine Structures of Iron Ions in Hemoproteins

Energy levels and eigenfunctions of various \(S\) states for d 5 and d 6 in a ligand field of the tetragonal symmetry are calculated. Then the spin-orbit interaction is taken account of and the fine structures of ground \(S\) states, mainly those of high spin states, are investigated in order to give the basis to analyze magnetic measurements on hemoproteins. For Fe 3+ , the spin Hamiltonian D S Z 2 is derived from perturbation calculation and the values of ligand field parameters X , Y and Z are discussed from the experimental value of D for ferric myoglobin. Biquardratic terms of spin Hamiltonian are also derived. For Fe 2+ , temperature dependences of the effective magnetic moment are discussed in detail for various cases of ligand field strength. In ferrous hemoglobin, the lowest quintet state seems to be separated from other quintet states by energies much larger than the spin-orbit interaction and the ligand field seems to be considerably different from that in the ferric form.