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Ultrafast electron transfer dynamics of a Zn(II)porphyrin-viologen complex revisited: S2 vs S1 reactions and survival of excess excitation energy.
Petersson, Jonas; Eklund, Mattias; Davidsson, Jan; Hammarström, Leif.
Afiliação
  • Petersson J; Chemical Physics Group, Department of Photochemistry and Molecular Science, Uppsala University, Box 523, SE-751 20 Uppsala, Sweden.
J Phys Chem B ; 114(45): 14329-38, 2010 Nov 18.
Article em En | MEDLINE | ID: mdl-20192180
The photoinduced electron transfer reactions in a self-assembled 1:1 complex of zinc(II)tetrasulphonatophenylporphyrin (ZnTPPS(4-)) and methylviologen (MV(2+)) in aqueous solution were investigated with transient absorption spectroscopy. ZnTPPS(4-) was excited either in the Soret or one of the two Q-bands, corresponding to excitation into the S(2) and S(1) states, respectively. The resulting electron transfer to MV(2+) occurred, surprisingly, with the same time constant of τ(FET) = 180 fs from both electronic states. The subsequent back electron transfer was rapid, and the kinetics was independent of the initially excited state (τ(BET) = 700 fs). However, ground state reactants in a set of vibrationally excited states were observed. The amount of vibrationally excited ground states detected increased with increasing energy of the initial excited state, showing that excess excitation energy survived a two-step electron transfer reaction in solution. Differences in the ZnTPSS(•3-)/MV(•+) spectra suggest that the forward electron transfer from the S(2) state at least partially produces an electronically excited charge transfer state, which effectively suppresses the influence of the inverted regime. Other possible reasons for the similar electron transfer rates for the different excited states are also discussed.

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: J Phys Chem B Assunto da revista: QUIMICA Ano de publicação: 2010 Tipo de documento: Article País de afiliação: Suécia País de publicação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: J Phys Chem B Assunto da revista: QUIMICA Ano de publicação: 2010 Tipo de documento: Article País de afiliação: Suécia País de publicação: Estados Unidos