Synthesis and photophysical properties of porphyrins containing viologen units for ultrafast molecular photonics

Several 5,15-diarylporphyrin derivatives containing viologen units as an electron acceptor for ultrafast intramolecular electron transfer have been synthesized. The fluorescence of the porphyrin–viologen linked systems was appreciably quenched by the attached viologens. In accordance with this, the formation of a charge-separated state was observed upon excitation with a femtosecond (fs) laser at 400 nm. The rate of electron transfer and back transfer was controlled by the different length of alkyl chain spacers between porphyrin and viologen. Attempts to use these porphyrin molecules as a thin film component of ultrafast parallel data processing by guided wave mode geometry were limited by gradual deterioration upon repeated fs laser excitation.