Nature and mechanism of high spin–low spin crossovers and the existence of intermediate spin states

Abstract

Temperature- and pressure-dependent spectroscopic and magnetic, and X-ray crystallographic studies show that, in some Fe^III and Fe^II crossover systems, rapid thermal equilibria occur between high spin, low spin and sometimes intermediate spin states, with solvent molecules sometimes inducing specific spin states; it is of relevance to biological systems that the single ‘spin-mixed’ state model is inapplicable in every well studied case.