Electronic States of Iron

Abstract

The description of the electronic states of iron in hemoglobin has been approached through crystal field theory and molecular orbital theory, and by a combination of the two, which is known as ligand field theory. Each approach provides certain insights, though none is entirely satisfactory. In all cases, however, symmetry is of paramount importance. We shall therefore devote this chapter to a summary of the results pertaining to Fe²⁺ and Fe³⁺ which are largely consequences of the symmetry of the environment in which the ion is immersed. A natural starting point is the free ion whose symmetry is that of the full rotation group.