Hydrogen-bonding dynamics in photoinduced electron transfer in ferrocene - Quinone linked dyad with a rigid amide spacer

A newly designed ferrocene-quinone dyad with an amide space (Fc-Q) is employed to examine formation of the hydrogen bonding in the one-electron reduced form (Q•-) and the dynamics in the photoinduced electron-transfer reaction from the ferrocene to the quinone moiety. Photoexcitation of the Q moiety in Fc-Q in deaerated PhCN with 388 nm results in intramolecular electron transfer from Fc to the singlet excited state of Q to produce Fc⁺-Q•^- without changing the conformation (<1 ps), followed by hydrogen bond formation with the amide proton of the spacer (τ =∼ 5 ps). The resulting radical ion pair decays via a back electron transfer to the ground state at a longer time scale with a rate constant of 2.6 × 10 8 s^-1.