Structures and Properties of Spherical 90-Vertex Fullerene-Like Nanoballs

By applying the proper stoichiometry of 1:2 to [(CpFe)-Fe-R(eta(5)-P-5)] and CuX (X = Cl, Br) and dilution conditions in mixtures of CH3CN and solvents like CH2Cl2, 1,2-Cl2C6H4. toluene, and THF, nine spherical giant molecules having the simplified general formula [(CpFe)-Fe-R(eta(5)-P-5)]@[{(CpFe)-Fe-R(eta(5)-P-5}(12){CuX}(25)(CH3CN)(10)] (Cp-R = eta(5)-C5Me5 (Cp*); eta(5)-C5Me4Et (Cp-Et); X = Cl, Br) have been synthesized and structurally characterized. The products consist of 90-vertex frameworks consisting of non-carbon atoms and forming fullerene-like structural motifs. Besides the mostly neutral products, some charged derivatives have been isolated. These spherical giant molecules show an outer diameter of 2.24 (X = Cl) to 2.26 nm (X = Br) and have inner cavities of 1.28 (X = Cl) and 1.20 nm (X = Br) in size. In most instances the inner voids of these nanoballs encapsulate one molecule of [Cp*Fe(eta(5)-P-5)], which reveals preferred orientations of pi-pi stacking between the cyclo-P-5 rings of the guest and those of the host molecules. Moreover, pi-pi and sigma-pi interactions are also found in the packing motifs of the balls in the crystal lattice. Electrochemical investigations of these soluble molecules reveal one irreversible multi-electron oxidation at E-p = 0.615 V and two reduction steps (-1.10 and -2.0 V), the first of which corresponds to about 12 electrons. Density functional calculations reveal that during oxidation and reduction the electrons are withdrawn or added to the surface of the spherical nanomolecules, and no Cu2+ species are involved.