We employed both femtosecond fluorescence up-conversion and transient absorption techniques with ∼150 fs time resolution to study the excited-state deactivation process of an intra-molecular charge transfer model compound, 4-(ferrocen-1-yl)benzylidene-malononitrile (Fc-ph-DCV), which consists of ferrocene (Fc) unit as an electron donor, dicyanovinly (DCV) as an electron acceptor and phenyl (ph) ring as the central bridge. The results showed that after photoexcitation into the higher excited S2 state, ultrafast internal conversion into S1 takes place. The rate of S2 → S1 internal conversion is markedly faster (with a typical time of 120 fs ± 20 fs) than the diffusive solvation process. On the other hand, the lifetime of the relaxed S1 state was strongly dependent on the solvent polarity, changing from 40 to 50 ps in acetonitrile to ∼20 ps in cyclohexane. Time-resolved fluorescence data also showed subpicosecond transient component that is attributable to the spectral relaxation caused by solvation and/or vibrational relaxation in the S1 state.
- Charge transfer
- Time-resolved fluorescence
- Ultrafast internal conversion
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry