Spin-forbidden reactions: computational insight into mechanisms and kinetics

Many chemical reactions involve one or more changes in the total electronic spin of the reacting system as part of one or more elementary steps. Computational and theoretical methods that can be used to understand such reaction steps are described, and a number of recent examples are highlighted. A particularly strong focus is given to general rules that govern multistep reactions of this type. The two most important rules are (1) that spin-state change without change in atom connectivity, or spin crossover, is facile and rapid, at least when it is exothermic; and (2) that reactions involving spin-state change and changes in atom connectivity tend to prefer stepwise mechanisms in which spin crossover steps alternate with spin-allowed bond-making and breaking steps. (C) 2013 John Wiley & Sons, Ltd. WIREs Comput Mol Sci 2014, 4:1-14. doi: 10.1002/wcms.1154 The authors have declared no conflicts of interest in relation to this article. For further resources related to this article, please visit the WIREs website.