| The photophysics of higher fullerenes remain poorly characterized, partly because they may exist in many isomeric structures that are difficult to isolate. This project concerns the properties of C84 isomers. Using recycling HPLC methods, we separated a sample of purified C84 into three fractions. The first contains a mixture of the three most abundant isomers---D 2 (IV), D2d (II), and Cs (a). The second and third peaks were found to contain the C2 and Cs (b) isomers, respectively. A kinetics-based method was used to find the effective molar absorptivities of these fractions. Sensitive transient absorption measurements following optical excitation reveal widely differing triplet state lifetimes among these isomers. Quenching studies indicate that one C84 isomer has a triplet state energy below that of oxygen's 1Delta g state, while the others have higher energies. Further results, including fluorescence spectra and variable-temperature triplet decay kinetics, will also be presented. |
