Bimolecular reactions, spin state changes

The study of the dynamics of spin-state changes is important for the understanding of the kinetics of bimolecular electron transfer reactions ° and racemization and isomerization processes (Sec. 7.5.1). Low spin — high spin equilibria, often attended by changes in coordination numbers, are observed in some porphyrins and heme proteins, although their biological significance is, as yet, uncertain. 

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