ChemInform Abstract: Dynamics of Spin Equilibria in Metal Complexes

Abstract

Publisher Summary This chapter examines the dynamics of spin-equilibrium processes, principally from studies in solutions. The properties of the complexes that are relevant to the dynamics studies are reviewed. The techniques used to observe these rapid processes are also described in the chapter. The chapter presents some aspects of solid-state dynamics and describes some implications for the description of intersystem crossing processes in excited states and for spin equilibria in heme proteins. Many of the complexes that occur in spin equilibrium possess ligands with complicated structures. Trivial abbreviations are used, with structural formulas presented in the table. Generally the complexes are of low symmetry, but in the description of their electronic structure idealized symmetries are assumed and the appropriate term symbols are used accordingly. Some of the concepts, which are used to describe intramolecular spin equilibria, can be extended to the description of these coordination-spin equilibria. Examples include equilibria among four-, five-, and six-coordinate nickel (II) complexes and equilibria involving coordination number changes in iron porphyrin complexes and in heme proteins. Anomalous magnetic susceptibility is the characteristic feature of spin-equilibrium complexes. The Evans nuclear magnetic resonance (NMR) method gives excellent results provided adequate care is taken. There have been very few reports of the Raman spectra of spin-equilibrium complexes.