Femtosecond dynamics of metalloporphyrins: electron transfer and energy redistribution

Femtosecond-resolved, real-time dynamics of the low-lying excited state 2Q(π,π*) of cobalt(II) tetraphenylporphyrin are reported in different solvents of varying polarity and structure. The dependence of the dynamics on the probing wavelength and on the metal and porphyrin substitution was also investigated. The decay in the π system of the porphyrin occurs with a lifetime of 220 fs in benzene, while a second process with a lifetime of 1.8 ps is consistent with a proposed model for intramolecular charge separation: porphyrin a2u(π)→Co(dz2). The dynamics of the charge transfer state is influenced by the solventsʹ polarity and coordination ability.