Poly(perfluoroalkylation) of metallic nitride fullerenes reveals addition-pattern guidelines: synthesis and characterization of a family of Sc3N@C80(CF3)n (n = 2-16) and their radical anions.

A family of highly stable (poly)perfluoroalkylated metallic nitride cluster fullerenes was prepared in high-temperature reactions and characterized by spectroscopic (MS, (19)F NMR, UV-vis/NIR, ESR), structural and electrochemical methods. For two new compounds, Sc(3)N@C(80)(CF(3))(10) and Sc(3)N@C(80)(CF(3))(12,) single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental ((19)F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc(3)N@C(80)(CF(3))(n) (n = 2-16). Electrochemical studies revealed that Sc(3)N@C(80)(CF(3))(n) derivatives are easier to reduce than Sc(3)N@C(80), the shift of E(1/2) potentials ranging from +0.11 V (n = 2) to +0.42 V (n = 10). Stable radical anions of Sc(3)N@C(80)(CF(3))(n) were generated in solution and characterized by ESR spectroscopy, revealing their (45)Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc(3)N@C(80) making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance.

Sc2(mu2-O) trapped in a fullerene cage: the isolation and structural characterization of Sc2(mu2-O)@C(s)6-C82 and the relevance of the thermal and entropic effects in fullerene isomer selection.

The new endohedral fullerene, Sc(2)(mu(2)-O)@C(s)(6)-C(82), has been isolated from the carbon soot obtained by electric arc generation of fullerenes utilizing graphite rods doped with 90% Sc(2)O(3) and 10% Cu (w/w). Sc(2)(mu(2)-O)@C(s)(6)-C(82) has been characterized by single crystal X-ray diffraction, mass spectrometry, and UV/vis spectroscopy. Computational studies have shown that, among the nine isomers that follow the isolated pentagon rule (IPR) for C(82), cage 6 with C(s) symmetry is the most favorable to encapsulate the cluster at T > 1200 K. Sc(2)(mu(2)-O)@C(s)(6)-C(82) is the first example in which the relevance of the thermal and entropic contributions to the stability of the fullerene isomer has been clearly confirmed through the characterization of the X-ray crystal structure.

Preferential encapsulation and stability of La(3)N cluster in 80 atom cages: experimental synthesis and computational investigation of La(3)N@C(79)N.

We report the synthesis and electronic stabilization of La(3)N@C(79)N. Unsuccessful efforts to encapsulate bulky La(3)N clusters in small C(80) cages have been attributed to large ionic radii. The preferred species for La(3)N clusters in all-carbon cages is La(3)N@C(96). A surprising finding is the synthesis of La(3)N@C(79)N, a new metallofullerene present in higher abundance than La(3)N@C(96). This reduction in cage size from 96 to 80 atoms reflects the significance and role of electronic effects. To understand the geometric and electronic properties of this first metallic nitride azafullerene (M(3)N@C(79)N, M = La), density functional theory (DFT) investigations were performed on a number of isomers. Results indicate a preferred N-substitution at the 665 junction site on the cage in lieu of a 666 substitution. The relative stabilities of different isomers can be well reproduced by using the minimum distance between the metal atom and the nitrogen atom of the cage (R(N'M)(min)). Long R(N'M)(min) values indicate distant contacts between six atoms that bear significantly large positive charges: the three metal atoms and the three carbon atoms bonded with the nitrogen atom in the cage, which are favored. These results suggest a dominant electronic effect on the stabilities of metalloazafullerenes. Interestingly, spin densities of the 665 substitution isomers of La(3)N@C(79)N are located predominantly in the metal cluster, while spin densities of the 666 substitution isomers are primarily on the cage.

Selective complexation and reactivity of metallic nitride and oxometallic fullerenes with Lewis acids and use as an effective purification method.

Metallic nitride fullerenes (MNFs) and oxometallic fullerenes (OMFs) react quickly with an array of Lewis acids. Empty-cage fullerenes are largely unreactive under conditions used in this study. The reactivity order is Sc(4)O(2)@I(h)-C(80) > Sc(3)N@C(78) > Sc(3)N@C(68) > Sc(3)N@D(5h)-C(80) > Sc(3)N@I(h)-C(80). Manipulations of Lewis acids, molar ratios, and kinetic differences within the family of OMF and MNF metallofullerenes are demonstrated in a selective precipitation scheme, which can be used either alone for purifying Sc(3)N@I(h)-C(80) or combined with a final high-performance liquid chromatography pass for Sc(4)O(2)@I(h)-C(80), Sc(3)N@D(5h)-C(80), Sc(3)N@C(68), or Sc(3)N@C(78). The purification process is scalable. Analysis of the experimental rate constants versus electrochemical band gap explains the order of reactivity among the OMFs and MNFs.