Separation and Photophysical Properties of C_(84) Minor Isomer D_(2d)(I)

摘要

Higher fullerenes like C_(84) present a rich variety of photophysical properties, due to their many distinct geometric isomers. However, this multitude of isomers, along with their similar chromatographic properties, creates difficulties in purifying and characterizing specific species of C_(84). In this paper, we present the application of an alternating-column HPLC technique to resolve C_(84) isomers. We find this technique presents markedly higher separation efficiency than recycling HPLC. Subsequent photophysical analysis of a previously uncharacterized isomer of C_(84), {D_(2d)(I)}, shows its transient absorbance properties differ from those of other C_(84) isomers, in terms of both spectral features (with maxima at 620 and 840 nm) and lifetime (ca. 45.6 μs). Singlet-oxygen quenching experiments demonstrate that the T_1 energy of D_(2d)(I) lies below 7880 cm~(-1). Finally, ground-state absorptivity of D_(2d)(I) has been characterized via quenching experiments with palladium octaethylporphyrin, showing an ε = 21,400 M~(-1) cm~(-1) at a local maximum of 590 nm.