Marcus equilibrium-rate theory, reaction coordinate

The rationalization of PER by Marcus is based on a simple model of the reaction profile, that of two intersecting parabolas (Pigure 5.10) [35]. In most applications of the Marcus equilibrium-rate theory, the reaction coordinate is a normalized quantity between 0 and 1, measuring in a generalized way the progress of reaction it is usually poorly defined from a geometrical, structural point of view. Indeed, when the word structure is used in works on PER, it refers mainly to the connectivity... 

In the o.s. reaction, the ion pair A+ - B is formed in a first step. The corresponding equilibrium constant can usually be obtained from simple electrostatic models. In this "ideal" case specific chemical interactions can be neglected and the rate constant of the E.T. step follows the theory of R.A. Marcus (see for example Marcus, 1975, or Cannon, 1980). In the i.s. reaction each of the three steps in reaction (9.2) may determine the reaction rates. The lability of the coordinated ligands at the... 

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