Fulleropyrrolidine Derivatives Polyarylamine Synthesis And Photophysical Photochemical Properties

Fullerenes are characterized by remarkably strong electron-accepting properties and small reorganization energies. As electron-acceptors, they can connect the organic donors to form the fullerene-based donor-acceptor dyads, which can occur the photoinduced charge-separated states. This has, for example, been demonstrated from the observation of intermolecular quenching of both the excited singlet and triplet state of fullerenes by various electron donor species and by the observation of various photoreactions that can be formulated to emerge from primary electron transfer. So the solar cells with the fullerene derivatives as the photosensitive layer materials began to be applied to the industry. This makes the design and synthesis of fullerene derivatives bearing the photoelectric function become more and more attractive.The synthesis of several donor-bridge-fullerene (acceptor) systems has been reported, but in only a few cases has photoinduced intramolecular charge separation been reported to occur. The lifetime of charge-separated (CS) states is highly sensitive to the energy of the CS state, the type of linkage between the donor and acceptor molecules, and also the solvent. The polyamine-fullerene linked systems exhibit small reorganization energies, which can accelerate photoinduced charge separation (CS) and retard charge recombination (CR) as achieved in photosynthesis. Along this line, in this paper, we synthesized three N- methyl- 2-pyrrolo[3,4]- C60 derivatives by 1,3-dipolar cycloaddition under microwave irradiation, in which C60 and amine donors are covalently bonded with short linkage. The structures of these compounds were characterized by MS,1H NMR, IR, UV-Vis spectra. Fluorescence spectra showed that the three compounds were fluorescent at room temperature. Photoinduced intramolecular electron transfer processes between fullerene and carbazole have been studied by nanosecond laser flash photolysis. The charge-separated state C60·--Cz·- was observed in the near-IR region and its life was 0.28 μ s. The rates and efficiencies of the CS processes were measured by time-resolved fluorescence measurements with changing solvent polarity. The origin of the long lifetimes of the CS state has been revealed by the Marcus parametersexperimentally evaluated from the temperature dependence of the CR rate constants. We also reported semiempirical AMI method and density functional theory calculations (B3LYP/6-31G(d)) that offered optimized structures of the compounds. The results show that the HOMOs were mainly localized on C60, while the LUMOs were mainly localized on the substituents. This indicated that the electrons were easy to transfer from the occupied orbitals of donors to the virtual orbital of the acceptors, i.e. to excited states. On the basis of the equilibrium geometry optimized by B3LYP/6-31G(d) method, we employed the ZINDO method to obtain the electronic spectrum of fulleropyrrolidine 1. The calculated results were essentially consistent with experimental values.