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 1a and 1b, which have one PhCD(2)- 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.