Photoinduced energy and electron transfer in porphyrin-anthraquinone dyads bridged with a triazine group

Porphyrin-anthraquinone dyads containing a triazine group as linker were synthesized and characterized by 1H NMR, UV–visible, fluorescence and transient spectra and ESI-MS. Absorption spectra revealed that there was no appreciable interaction between the ground-state porphyrin moiety and the ground-state anthraquinone moiety. Fluorescence spectra illustrated that energy transfer takes place from the excited anthraquinone moiety to the porphyrin moiety when excited at 250 nm, whilst efficient electron transfer occurs from the singlet excited porphyrin moiety to the anthraquinone moiety in the case of excitation at 420 nm. A long-lived, charge-separated state H2P+–EQ− was observed by transient absorption spectra with a lifetime of 1.42 μs and 1.33 μs. These photochemical events were explained from electrochemical studies and suggest that the compounds have the ability to simulate electron transfer from chlorophylls to electron acceptors.