Abstract
We employed both femtosecond fluorescence up-conversion and transient absorption techniques with similar to 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 S(2) state, ultrafast internal conversion into S(1) takes place. The rate of S(2) -> S(1) 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 S(1) state was strongly dependent on the solvent polarity, changing from 40 to 50 ps in acetonitrile to similar 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 S(1) state. Published by Elsevier B. V.