426230-66-2Relevant articles and documents
Metal ion-promoted intramolecular electron transfer in a ferrocene-naphthoquinone linked dyad. Continuous change in driving force and reorganization energy with metal ion concentration
Okamoto, Ken,Imahori, Hiroshi,Fukuzumi, Shunichi
, p. 7014 - 7021 (2003)
Thermal intramolecular electron transfer from the ferrocene (Fc) to naphthoquinone (NQ) moiety occurs efficiently by the addition of metal triflates (Mn+: Sc(OTf)3, Y(OTf)3, Eu(OTf)3) to an acetonitrile solution of a ferrocene-naphthoquinone (Fc-NQ) linked dyad with a flexible methylene and an amide spacer, although no electron transfer takes place in the absence of Mn+. The resulting semiquinone radical anion (NQ.-) is stabilized by the strong binding of Mn+ with one carbonyl oxygen of NQ.- as well as hydrogen bonding between the amide proton and the other carbonyl oxygen of NQ.-. The high stability of the Fc+-NQ.-/Mn+ complex allows us to determine the driving force of electron transfer by the conventional electrochemical method. The one-electron reduction potential of the NQ moiety of Fc-NQ is shifted to a positive direction with increasing concentration of Mn+, obeying the Nernst equation, whereas the one-electron oxidation potential of the Fc moiety remains the same. The driving force dependence of the observed rate constant (kET) of Mn+-promoted intramolecular electron transfer is well evaluated in light of the Marcus theory of electron transfer. The driving force of electron transfer increases with increasing concentration of Mn+ [Mn+], whereas the reorganization energy of electron transfer decreases with increasing [Mn+] from a large value which results from the strong binding between NQ.- and Mn+.
