(Invited) Separation and Photophysical Properties of C84 Minor Isomer D2d(I)

Abstract

Higher fullerenes such as C84 present a rich variety of photophysical properties, due to their abundance of distinct geometric isomers. However, this multitude of isomers, along with their similar chromatographic properties, also creates difficulties in purifying and characterizing specific species of C84. In this paper, we present the application of an alternating-column HPLC technique to resolve C84 isomers. We find that this technique presents markedly higher separation efficiency than the recycling HPLC method. Subsequent photophysical analysis of a previously uncharacterized isomer of C84, D2d(I), shows its transient absorbance properties clearly differ from those of other C84 isomers, in terms of both its spectral features (with maxima at 620 and 840 nm) and lifetime (ca. 45.6 μs). Singlet-oxygen quenching experiments demonstrate that the T1 energy of D2d(I) lies below 7880 cm-1. Finally, the ground-state absorptivity of the D2d(I) isomer 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.