Magnetism of Mixed-Valence Compounds

Abstract

Mixed valence compounds exhibit a wide range of magnetic properties. These properties range from simple diamagnetism which is temperature independent and which may be estimated rather accurately from Pascal’s constants, to Curie-Weiss paramagnetism, to exceptionally complicated behavior which may arise from single ion effects, exchange coupling interactions, or both. Studies of the magnetic properties of mixed valence compounds often yield valuable information concerning the chemical nature and electronic structure of the substances. In this chapter, results ofrepresentative studies of magnetic properties of mixed valence compounds will be described with the aim of illustrating the phenomena which are exhibited and the manner in which the results are used in the solution of chemical problems. Systems of discrete clusters, chains, sheets, and three dimensional polymeric materials will be discussed here. For the most part, these will be compounds in which metal ions are bridged by ligands such as halides,oxide, pyrazine, and other ions and small molecules, although representative results for compounds containing metal-metal bonds will be included. Because of space limitations and a recent review on the subject, results on mixed valence metalloproteins and enzymes will not be covered.