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Successful isolation and unambiguous crystallographic assignment of a series of higher carbide cluster metallofullerenes present new insights into the molecular structures and cluster-cage interactions of endohedral metallofullerenes. These new species are identified as La2C2@C2(41)-C90, La2C2@D3(85)-C92, La2C2@C1(132)-C94, La2C2@C2(157)-C96, and La2C2@C1(175)-C98. This is the first report for these new cage structures except for D3(85)-C92. Our experimental and theoretical results demonstrate that La2C92–106 are more inclined to exist stably in the carbide form La2C2@C90–104 rather than as the dimetallofullerenes La2@C92–106, which are rationalized by considering a synergistic effect of inserting a C2 unit into the cage, which ensures strong metal–cage interactions by partially neutralizing the charges from the metal ions and by fulfilling the coordination requirement of the La3+ ions as much as possible. [ABSTRACT FROM AUTHOR]

Recently, several experiments have demonstrated high chemical reactivity of the sumanene-type hexagon in Sc2C2@C82. To further uncover its reactivity, the Diels-Alder reaction to all the nonequivalent C-C bonds of C82 and Sc2C2@C82 has been investigated by density functional theory calculations. For the free fullerene, the [5,6] bond 7 is the thermodynamically most favored, whereas the addition on the [6,6] bond 3 has the lowest activation energy. Diels-Alder reaction has no preference for addition sites in the sumanene-type hexagon. However, in the case of the endohedral fullerene, the [6,6] bond 19 in the special hexagon becomes the most reactive site according to both kinetic and thermodynamic considerations. Further analyses reveal that bond 19 in Sc2C2@C82 exhibits the shortest bond length and third largest π-orbital axis vector. In addition, the LUMOs of bond 19 are also symmetry-allowed to interact with butadiene. [ABSTRACT FROM AUTHOR]

Among the very recently reported dimetallic oxide fullerenes Sc2O@C2n (n = 35-47), a representative Sc2O@C78 still lacks of further characterizations. Herein, a systematical investigation on Sc2O@C78 has been performed by density functional theory combined with statistical thermodynamic studies. Two isolated pentagon rule (IPR) satisfying isomers, Sc2O@D3h(24109)-C78 and Sc2O@C2v(24107)-C78, are disclosed to possess prominent thermodynamic stabilities at the temperature region of fullerene formation. Significantly, these two structures are related by a single Stone-Wales transformation. Moreover, bonding critical points, bond orders, and delocalization indices have been analyzed to uncover covalent interactions in both isomers. In addition, 13C NMR spectra and UV-vis-NIR adsorptions of the two stable structures are introduced to assist experimental identification and characterization in the future. [ABSTRACT FROM AUTHOR]

The bis(μ-oxo) dimeric complexes {AriPr8OM(μ-O)}2 (AriPr8 = C6H-2,6-(C6H2-2,4,6-iPr3)2-3,5-iPr2; M = Fe (1), Co (2)) were prepared by oxidation of the M(I) half-sandwich complexes {AriPr8M(η6-arene)} (arene = benzene or toluene). Iron species 1 was prepared by reacting {AriPr8Fe(η6-benzene)} with N2O or O2, and cobalt species 2 was prepared by reacting {AriPr8Co(η6-toluene)} with O2. Both 1 and 2 were characterized by X-ray crystallography, UV-vis spectroscopy, magnetic measurements, and, in the case of 1, Mössbauer spectroscopy. The solid-state structures of both compounds reveal unique M2(μ-O)2 (M = Fe (1), Co(2)) cores with formally three-coordinate metal ions. The Fe···Fe separation in 1 bears a resemblance to that in the Fe2(μ-O)2 diamond core proposed for the methane monooxygenase intermediate Q. The structural differences between 1 and 2 are reflected in rather differing magnetic behavior. Compound 2 is thermally unstable, and its decomposition at room temperature resulted in the oxidation of the AriPr8 ligand via oxygen insertion and addition to the central aryl ring of the terphenyl ligand to produce the 5,5′-peroxy-bis[4,6-iPr2-3,7-bis(2,4,6-iPr3-phenyl)oxepin-2(5H)-one] (3). The structure of the oxidized terphenyl species is closely related to that of a key intermediate proposed for the oxidation of benzene. [ABSTRACT FROM AUTHOR]

Tunneling field-effect transistors (FETs) have been intensely explored recently due to its potential to address power concerns in nanoelectronics. The recently discovered graphene nanoribbon (GNR) is ideal for tunneling FETs due to its symmetric bandstructure, light effective mass, and monolayer-thin body. In this work, we examine the device physics of p-i-n GNR tunneling FETs using atomistic quantum transport simulations. The important role of the edge bond relaxation in the device characteristics is identified. However, the device has ambipolar I−Vcharacteristics, which are not preferred for digital electronics applications. We suggest that using either an asymmetric source-drain doping or a properly designed gate underlap can effectively suppress the ambipolar I−V. A subthreshold slope of 14mV/dec and a significantly improved on−off ratio can be obtained by the p-i-n GNR tunneling FETs. [ABSTRACT FROM AUTHOR]