Pentagonal-Dodecahedral La2 Charge Density in [80-Ih]Fullerene: La2@C80

No Abstract     

Conductivity and field effect transistor of La2@C80 metallofullerene

We first demonstrate a field-effect-transistor operation of dimetallofullerene La2@C80 with the icosahedral cage symmetry. The thin-film device showed an n-type behavior with a mobility of 1.1 x 10-4 cm2/V s at room temperature under high vacuum. Taking the nature of LUMO into account, the n-type behavior indicates an occurrence of carrier conduction through encapsulated La ions. The low mobility, suggesting an intermolecular hopping mechanism, is ascribed to the intrinsic and extrinsic reasons, which are discussed in the text.     

Tunable charge-transport properties of I(h)-C80 endohedral metallofullerenes: investigation of La2@C80, Sc3N@C80, and Sc3C2@C80

Fullerene crystals or films have drawn much interest because they are good candidates for use in the construction of electronic devices. The results of theoretical calculations revealed that the conductivity properties of I(h)-C(80) endohedral metallofullerenes (EMFs) vary depending on the encapsulated metal species. We experimentally investigated the solid-state structures and charge-carrier mobilities of I(h)-C(80) EMFs La(2)@C(80), Sc(3)N@C(80), and Sc(3)C(2)@C(80). The thin film of Sc(3)C(2)@C(80) exhibits a high electron mobility μ = 0.13 cm(2) V(-1) s(-1) under normal temperature and atmospheric pressure, as determined using flash-photolysis time-resolved microwave conductivity measurements. This electron mobility is 2 orders of magnitude higher than the mobility of La(2)@C(80) or Sc(3)N@C(80).     

Two-dimensional hopping motion of encapsulated La atoms in silylated La(2)@C(80)

The (139)La NMR study of the exohedrally functionalized derivatives of La(2)@C(80) metallofullerene, La(2)@C(80)(Ar(2)Si)(2)CH(2) (: Ar = Mes, Mes = mesityl, : Ar = Dep, Dep = 2,6-diethylphenyl), reveal that the two La atoms hop between two sites along the equator of the C(80) cage.     

Regioselective bis-functionalization of endohedral dimetallofullerene, La2@C80: extremal La-La distance

Bis-functionalization of endohedral metallofullerene La(2)@C(80) by carbene addition is reported herein. Adducts were characterized using spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for bisadduct La(2)@C(80)(CClPh)Ad (3, Ad = adamantylidene) revealed that both carbene additions occur at the 6,6-bond junction on the C(80) cage with ring cleavages and that La atoms are positioned collinearly with spiro carbons. It is noteworthy that the La-La distance in 3 is highly elongated by carbene bis-functionalization compared to the distance in pristine La(2)@C(80) and reported functionalized derivatives. The metal positions were confirmed through density functional calculations.     

La2@C72 and Sc2@C72: computational characterizations

The La2@C72 and Sc2@C72 metallofullerenes have been characterized by systematic density functional computations. On the basis of the most stable geometry of 39 C72 hexaanions and the computed energies of the best endofullerene candidates, the experimentally isolated La2@C72 species was assigned the structure coded #10611. The good agreement between the computed and the experimental 13C chemical shifts for La2@C72 further supports the literature assignment (Kato, H.; Taninaka, A.; Sugai, T.; Shinohara, H. J. Am. Chem. Soc. 2003, 125, 7782). The geometry, IR vibrational frequencies, and 13C chemical shifts of Sc2@C72 were predicted to assist its future experimental characterization.     

Synthesis and structural characterization of endohedral pyrrolidinodimetallofullerene: La2@C80(CH2)2NTrt

The endohedral pyrrolidinodimetallofullerene, La2@C80(CH2)2NTrt (Trt = triphenylmethyl), was successfully synthesized and characterized. X-ray crystallographic and NMR spectroscopic analyses reveal that two La atoms in the 6,6-adduct are localized at the stable site on the mirror plane. Theoretical calculation also suggests the localization of two La atoms in the 6,6-adduct.     

Coordinative Interactions between Porphyrins and C60, La@C82, and La2@C80

For the first time, a C₆₀ derivative ( 1 ) and two different lanthanum metallofullerene derivatives, La@C₈₂Py ( 2 ) and La₂@C₈₀Py ( 3 ), that feature a pyridyl group as a coordination site for transition‐metal ions have been synthesized and integrated as electron acceptors into coordinative electron‐donor/electron‐acceptor hybrids. Zinc tetraphenylporphyrin ( ZnP ) served as an excited‐state electron donor in this respect. Our investigations, by means of steady‐state and time‐resolved photophysical techniques found that electron transfer governs the excited‐state deactivation in all of these systems, namely 1/ZnP , 2/ZnP , and 3/ZnP , whereas, in the ground state, notable electronic interactions are lacking. Variation of the electron‐accepting fullerene or metallofullerene moieties provides the incentive for fine‐tuning the binding constants, the charge‐separation kinetics, and the charge‐recombination kinetics. To this end, the binding constants, which ranged from log K_assoc=3.94–4.38, are dominated by axial coordination, with minor contributions from the orbital overlap of the curved and planar π systems. The charge‐separation and charge‐recombination kinetics, which are in the order of 10¹⁰ and 10⁸ s^?1, relate to the reduction potential of the fullerene and metallofullerenes, respectively.