Synthesis and photophysical properties of porphyrin-linked C-60 dyads

C-60 has been covalently linked to the mesophenyl ring of zincporphyrin at para, meta, and ortho positions with amido groups to elucidate intramolecular photophysical properties of porphyrin-C-60 linked systems. Irrespective of the linking mode between the two chromophores, photoinduced charge separation (CS) and subsequent charge recombination (CR) were observed in a series of zincporphyrin-C-60 dyads by picosecond fluorescence lifetime measurements and time-resolved transient absorption spectroscopy. Zincporphyrin-linked quinone has also been designed and synthesized to evaluate the size effect of fullerene in electron transfer (ET). Accelerated CS and decelerated CR were observed in zincporphyrin-C-60 dyads compared with the corresponding porphyrin-linked quinone. The result is explained by the smaller reorganization energy in C-60 compared with that in benzoquinone.