A Room-Temperature Fluorescence Study of Organofullerenes: cis-1 Bisadduct with Unusual Blue-Shifted Emissions

C-60 derivatives have shown enhanced fluorescent emissions with respect to C-60 due to the lowering of molecular symmetry and have demonstrated promising potentials as novel organoelectronic materials for application in light-emitting diodes. Previous work has indicated that the fluorescent properties of functionalized C-60 are mainly affected by the addition patterns, rather than the nature of addends. However, no report on the fluorescence of C-60 cis-1 bisadducts, one of the most favorable types of C-60 bisadducts, has appeared up to date. Herein, the fluorescent properties of two structurally related C-60 cis-1 bisadducts of fullerooxazolines, 1 and 2, are examined at room temperature. It shows that a significant difference exists for the fluorescent spectra of 1 and 2, where 1 displays a rather strong unusual blue-shifted emission band, even though the two compounds have the same addition pattern. Monoadducts bearing individual addends of 1 and 2, along with la and 1b, which have one PhCD2- positioned either next to the C-60-N or C-60-O bond, are also examined in order to gain a better understanding of such difference. The results indicate that the unusual blue-shifted emissions for 1 are likely to originate from the vibrational interactions of the addends, suggesting that the fluorescent emissions of C-60 derivatives can be tuned not only by the addition patterns, but also by the nature of the adducts. Density functional theory and time-dependent density functional theory calculations are performed to rationalize the experimental observations.