Entropy and enthalpy contributions to the kinetics of proton coupled electron transfer to the Mn4O4(O2PPh2)6 cubane.
نویسندگان
چکیده
The dependence of rate, entropy of activation, and ((1)H/(2)H) kinetic isotope effect for H-atom transfer from a series of p-substituted phenols to cubane Mn4O4L6 (L = O2PPh2) (1) reveals the activation energy to form the transition state is proportional to the phenolic O-H bond dissociation energy. New implications for water oxidation and charge recombination in photosystem II are described.
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Kinetics of proton-coupled electron-transfer reactions
The kinetics of proton-coupled electron-transfer (pcet) reactions are reported for Mn4O4(O2PPh2)6, 1, and [Mn4O4(O2PPh2)6] , 1 , with phenothiazine (pzH). Both pcet reactions form 1H, by H transfer to 1 and by hydride transfer to 1 . Surprisingly, the rate constants differ by only 25% despite large differences in the formal charges and driving force. The driving force is proportional to the dif...
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ورودعنوان ژورنال:
- Physical chemistry chemical physics : PCCP
دوره 16 24 شماره
صفحات -
تاریخ انتشار 2014