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

C₆₀ derivatives have shown enhanced fluorescent emissions with respect to C₆₀ 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 C₆₀ are mainly affected by the addition patterns, rather than the nature of addends. However, no report on the fluorescence of C₆₀ <i>cis</i>-1 bisadducts, one of the most favorable types of C₆₀ bisadducts, has appeared up to date. Herein, the fluorescent properties of two structurally related C₆₀ <i>cis</i>-1 bisadducts of fullerooxazolines, <b>1</b> and <b>2</b>, are examined at room temperature. It shows that a significant difference exists for the fluorescent spectra of <b>1</b> and <b>2</b>, where <b>1</b> displays a rather strong unusual blue-shifted emission band, even though the two compounds have the same addition pattern. Monoadducts bearing individual addends of <b>1</b> and <b>2</b>, along with <b>1a</b> and <b>1b</b>, which have one PhCD₂– positioned either next to the C₆₀–N or C₆₀–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 <b>1</b> are likely to originate from the vibrational interactions of the addends, suggesting that the fluorescent emissions of C₆₀ 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.