Synthesis and photophysical properties of polyamides containing in-chain porphyrin and [60]fullerene

Conjugated polyamides containing porphyrin and 60]fullerene (C₆₀) in the main chain were prepared by a direct polycondensation of the 3′H,3″H-dicyclopropa1, 9:16, 17] 5, 6]fullerene-C₆₀-I _h -3′,3″-dicarboxylic acid and 5,15-bis(4-aminophenyl)-10,20-bis(3,5-dialkoxyphenyl)porphyrin in the presence of triphenyl phosphite and pyridine. Gel permeation chromatography (GPC) analysis of the polyamides showed the weight-average molecular weight was about 23,626–23,736, and the temperature at 5% weight loss determined by thermogravimetric analysis (TGA) was above 216 °C. The transmission electron microscopy (TEM) images displayed the regular one-dimensional linear arrays of the polyamides with lengths exceeded 200 nm. The photoinduced electron transfer from porphyrin to C₆₀ in the polyamides was observed in nanosecond laser-flash photolysis experiments at ambient temperature, which produced a charge-separated state (porphyrin radical cation–C₆₀ radical anion pair) with a lifetime as long as 40 μs. The calculated ratio of k _CS/k _CR was found to be 2.1 × 10⁴. They could have potential applications for photoelectronic devices, organic solar cells and so on.