Ultrafast photoinduced electron transfer from N,N,N ',N '-tetramethyl-p-phenylenediamine and N,N,N ',N '-tetramethylbenzidine to dichloromethane

作者：Boilet L; Buntinx G; Lefumeux C; Poizat O^*

来源：Journal of Photochemistry and Photobiology A: Chemistry , 2004, 163(3): 529-536.

DOI：10.1016/j.jphotochem.2004.02.011

• aromatic amines
• electron transfer
• time-resolved spectroscopy
• Raman

The photoinduced reaction of electron transfer (ET) from N,N,N',N' -tetramethyl-p-phenylenediamine (TMPD) and N,N,N',N'-tetramethylbenzidine (TMB) to the dichloromethane solvent has been studied by picosecond transient absorption and time-resolved resonance Raman spectroscopy. In neat CH2Cl2, "static" quenching of the lowest excited singlet state (S-1) of these amines is demonstrated. For TMPD, the reaction shows two kinetic contributions (tau(1) < 4 ps, tau(2) = 9.5 ps) that are ascribed to the fractions of excited molecules that react before and after they are vibrationally relaxed, respectively. A faster quenching reaction is observed for TMB (tau(1) < 4 ps) although it is less favourable energetically than for TMPD. This result is ascribed to a stronger acceptor-donor electronic coupling in the case of TMB, principally due a larger delocalization of the S I state donor orbital. The observation of a partial back electron transfer (9% yield) is tentatively explained as resulting from an evolution of the reaction product from an initial [TMB+., CH2Cl2-.] ion pair allowing charge recombination to a final form [TMB+. Cl-] inappropriate to back ET.

• 出版日期2004-5-21