Marcus normal region

Most photoinduced CS processes take place within the Marcus normal region. However, chaige recombination processes take place within the inverted region. Thus, the small reorganization eneigy of CHI will slow down CR processes. 

Figure 11 Dependence on driving force of first-order rate constant for back electron transfer from colloidal Sn02 films to covalently attached complexes. The variations indicate that the reactions occur in the Marcus normal region. The identities of the molecular redox couples, listed from highest driving force to lowest, are, Rulll/n (5-Cl-phen)2 (phos-...

In Fig. 13.13, the CR rates in the Marcus inverted region are much slower than the CS rates from both the singlet and triplet excited states in the Marcus normal region. This allows a subsequent electron transfer from an additional electron donor such as ferrocene (Fc) to ZnP+ in the triad molecule (Fc-ZnP+ -C60 ) to produce the final CS state, Fc+-ZnP-C60 , in competition with the back electron transfer in the initial CS states [41]. Such multi-step electron-transfer processes are expanded to the tetrad molecule (Fc-ZnP-H2P-C60) as shown in Fig. 13.16a [50], In the final CS state, Fc+-ZnP-H2P-C60 , charges are separated at... 

The discussion so far has focused on reactions in the Marcus-normal region , for which lAGoA I/Xr < 1. The regime in which A(jDA /Xr> 1 is most readily accessed by means of photochemical or pulsed radiolysis techniques. Photochemical techniques are very powerful, but they usually involve an initial photo-induced electron transfer process, and this requires pre-assembly of the reactants. In the context of outer-sphere electron transfer processes, such pre-assembly involves ground state ion pairs. 

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