Influence of organic acids on UV-Vis spectra of pyrrolidino-[60]fullerene derivatives

A pyrrolidino[60]fullerene 1 with pyrrolidine group was synthesized and characterized. The UV-Vis spectra showed that the blue shift of absorption peaks was first observed when strong organic acids such asp-toluene sulfonic or trifluoroacetic acid were added to the solution of pyrrolidino[60]fullerene 1 in dichloromethane. The results indicated that the pyrrolidino[60]fullerene derivatives without pyrrolidine group also possess the same phenomenon. Experiments and computation with the MOPAC 7.0 semi-empirical PM3 method demonstrated the reason that some energy gaps on [60] fullerene skeleton were increased because electronic charges on [60] fullerene framework transferred to pyrrolidine ring when strong organic acids were added into pyrrolidino[60]fullerene derivatives’ solution; as the result, the complexes could be formed and some absorption wavelengths blue shifted in the UV-Vis spectrum.