Rate saturation nonadiabaticity

Ill) Rate Determined by Conversion of Precursor to Successor Compiex. This is the case for the ordinary electron transfer discussed in earlier sections. However, even though all of the preceding steps may be rapid and no unfavorable preequilibria are involved, the rate constants for ordinary electron transfer saturate below the diffusion-controlled limit when the reaction is nonadiabatic (k, << 1). For example, when AG = 0 (the normal condition for a diffusion-controlled reaction), k, for a nonadia-... 

In a few systems, quenching rate constants tend toward saturation below the diffusion-controlled limit . This may be observed when the quenching reaction does not involve an electron-transfer process (e.g. , [ RuL3] -[Cr )] ), when the electron transfer is highly nonadiabatic, when the reactive form of the quencher is not the dominant form in solution (e.g. , [ RuL3] -[CU( )] , or when a substitutional or conformational change becomes rate determining. ... 

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