Femtosecond dynamics of electron transfer in a neutral organic mixed-valence compound

• Published in: Chemical physics 2008-05, Vol.347 (1), p.436-445
• Main Authors: Maksimenka, Raman, Margraf, Markus, Köhler, Juliane, Heckmann, Alexander, Lambert, Christoph, Fischer, Ingo
• Format: Article
• Language: English
• Subjects: Electron transfer; Femtosecond spectroscopy; Mixed-valence compound; Solvation dynamics; Transient absorption
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2007.11.022

In this article we report a femtosecond time-resolved transient absorption study of a neutral organic mixed-valence (MV) compound with the aim to gain insight into its charge-transfer dynamics upon optical excitation. The back-electron transfer was investigated in five different solvents, toluene, dibutyl ether, methyl- tert-butyl ether (MTBE), benzonitrile and n-hexane. In the pump step, the molecule was excited at 760 nm and 850 nm into the intervalence charge-transfer band. The resulting transients can be described by two time constant. We assign one time constant to the rearrangement of solvent molecules in the charge-transfer state and the second time constant to back-electron transfer to the electronic ground state. Back-electron transfer rates range from 1.5 × 10 12 s −1 in benzonitrile through 8.3 × 10 11 s −1 in MTBE, around 1.6 × 10 11 s −1 in dibutylether and toluene and to 3.8 × 10 9 s −1 in n-hexane.