A Carbon Nano‐Onion–Ferrocene Donor–Acceptor System: Synthesis, Characterization and Properties

Don't cry! The attachment of ferrocene moieties on the surface of carbon nano‐onions influences the electrochemical properties of these moieties and the photophysical properties of the carbon nano‐onions (see figure). Quantum chemical calculations confirm that the spectral properties of carbon nano‐onions depend on their size and the degree of functionalisation. magnified image We describe the synthesis and characterization of a novel ferrocene–carbon onion derivative, where ferrocene acts as an electron‐donating moiety, while the carbon nano‐onion (CNO) serves as the electron acceptor. CNOs were functionalized by 1,3‐dipolar cycloaddition and the resulting products were characterized by transmission electron microscopy, thermogravimetric analysis, Raman and energy dispersive spectroscopies. The electronic properties of the Fc–CNO derivative were investigated by electrochemical and photophysical techniques, complemented by quantum chemical calculations. On average, the CNOs have a spherical appearance with six shells. Functionalization saturates one carbon atom in 36 carbon atoms on the outer cage of the CNO. Through‐space interactions between the Fc moiety and the CNO core were detected electrochemically. Fluorescence was observed at low and high energies with an intrinsic decay that is faster at lower energies. Based on theory and experiment, we conclude that, after absorption of a photon at low energy, there is emission from CNOs characterized by larger external shells and a lower degree of functionalization. At high energy, emission comes from CNOs with smaller external shells and a higher degree of functionalization.